The aim of Daoism, Buddhism, meditation, Cognitive Behavioural Therapy, and every mindfulness program is to see truth. This process usually involves realizing that much of your "objective reality" is actually a constructed interpretation.
A friend does a good job of explaining this in the Buddhist tradition:
This isn't hippie mumbo jumbo. The Buddhist concept of the five Skandhas (form, sensation, perception, mental formations, consciousness) is an idea that dates back to thousands of years BC (Pali canon translation). The fact that it maps so well to modern neurobiology is remarkable. If you investigate a question using completely different tools, across societies and timespans, and come to a similar answer, you've probably found something useful.
A stimulus (sound of door creaking) hits the ear, reaches the thalamus, registers the automatic affect of fear via the amygdala in 20ms, and causes you to jump. 180ms later, the stimulus has been mediated by the cortex, which recognizes (through slower but more advanced cognition), that it was a friend entering the room, and your fear subsides. You recognize their face and begin a conversation. The entire experience starts as door atoms and sound waves, but eventually becomes rational meaning in your brain.
The first bit of this pathway, between stimulus and emotion, is notoriously difficult to control. It happens in milliseconds, and has been baked in by thousands of years of evolution, designed to keep you fed, safe, and keen on reproducing. Note that meditation always asks you to observe your emotions without judgement. No effective form of meditation or therapy ever asks you to stop the emotion from happening. It basically can't be done.
Even my favorite cognitive behavioural therapy textbook recognizes that you shouldn't try to intervene between stimulus and emotion. Instead, it recommends that you intervene at two other points: 1) examine the thought that arises from the emotion, and 2) look at the consequence of the action which results from those thoughts. Usually when someone says "control your emotions", they aren't saying "don't feel angry". They are saying "you may feel angry, but make better choices about what you do as a result".
Whether you choose religion, meditation, or CBT as your tool to address suffering, the ideal outcome is the same. You can never completely control the set of stimuli that the world will throw at you. Thus you want to configure your mental machinery so that regardless of the stimulus, you will form thoughts and actions which will lead to the best possible set of future outcomes. Run correctly over time, this cycle results in a life well lived. This "alignment" of machinery is the big old mess of what we call personality, character, temperament, etc. It defines who you are.
Depression - and most mental health disorders - are this machine, misconfigured. We perceive threats and insults where there are none, fail to recognize connections and opportunities when they are presented, and draw incorrect conclusions about the nature of what is possible. Stuck. Lonely. Hopeless. These are feelings which are simultaneously just "in your head", but also powerful enough to drive a person to end their life. They are both real and not real. What we do know is that they matter.
The word "disorder" is not pejorative: it is simply a description. A bike on high gear going up a steep hill is not bad: it's just misconfigured for the task at hand. A child who trusts nobody may be poorly configured for making friends in a high-trust society, but very sensibly configured for surviving in a world where they can only rely on themselves. An optimal configuration learned in one environment may be very unhelpful for another. The key insight from Bessel Van Der Kolk's The Body Keeps The Score is that trauma and symptoms of it are not indicators of the human body gone wrong. On the contrary, they are reflective of the mind's incredible ability to reconfigure itself for survival in extreme conditions.
Those of us who haven't seen horror to the degree that some of Bessel's patients have can still draw useful insight from his book. All childhood is trauma, and we all have experiences that have made us feel scared, helpless, humiliated, and dreadfully alone. Our brains have learned their current configuration over time from such events, alongside joy, hope, and comfort. It's very unlikely that the brain which we've landed on is perfectly suited for the future, or even the present.
It takes skill and patience to learn how your mental machinery operates, and to begin tweaking the pieces within yourself. This is the work that any good form of therapy or mindfulness meditation aims to do. This is also why a bad therapist can be such a harmful experience: they were supposed to be a fixer. Instead of concluding that your fixer is unskilled, you may draw the devastating conclusion that you yourself are unfixable. Once you're in that corner, it's a hard place to get out from.
It can take years to see progress - in fact, it will more likely be work that lasts a lifetime.
A psilocybin mushroom, then, is a curious thing. Nature has given us an organism which can blast that mental machinery apart on command. Scientific literature tells us that psilocybin mushrooms suppress the brain's default mode network. Simply put, it quiets the noise inside your mind and allows you to perceive the world with more presence, and less self-narrative and judgement.
People on shroom trips report feeling a renewed sense of wonder, of openness, and of connectedness with the world. You find yourself doing things like listening intensely to the crunch of tree bark under your feet. Or feeling like you're about to meld into the infinite universe. You start to see boundaries and definitions for what they are - arbitrary structures:
When people see some things as beautiful,
other things become ugly.
When people see some things as good,
other things become bad.
Being and non-being create each other.
Difficult and easy support each other.
Long and short define each other.
High and low depend on each other.
Before and after follow each other.
-Tao Te Ching (Mitchell translation)
Asserting the idea of "you" will seem as silly as trying to keep track of a specific raindrop in the middle of a thunderstorm. Feelings of failure, shame, guilt, and hopelessness start losing their soul-crushing weight. If such things exist, you can assess them for what they are: narrow conclusions that rely on so many preceding assumptions and judgements, none of which are objective truth.
"Magic" mushrooms aren't magic at all: if anything, they allow us to see reality more accurately, free of categorizations and judgements.
So why don't we all just walk around, permanently high on shrooms all the time? The problem is that reality is infinitely rich. Anyone who takes it in unfiltered would be completely overwhelmed. Our emotional and cognitive systems evolved to give us a way to triage information in an endlessly complex world. They zero us in on food, threats, and people to have sex with. Our brains are a filter through which a dimmed-down version of reality passes through at any given time, neatly packaged by our cognition so that we can make decisions and feel some sense of agency without going insane. Normally this is useful. But when that machine goes awry, as it does in depression, it becomes a self-reinforcing trap.
So then why is depression (or any mental disorder) so hard to escape? And why aren't mushrooms a magic solution?
Well, the brain may be plastic, but it requires enormous and deliberate work to mold. It is literally impossible to change things that you are not mindful of. And even when you are aware of something, that is different from being able to control it. On mushrooms I can see the triviality of my own ego. In moments of meditation, or strong emotional awareness, I can achieve this humility even in a "sober"* state. But it has by no means become a habit in my normal waking life. I still act out of ego most of the time, and I say stupid things as a result of it. There's a reason why psilocybin (or any drug, for that matter) has not rendered years of religious and philosophical tradition useless. There are no shortcuts to wisdom.
(*The use of the word sober here is funny, as sobriety usually implies a correct state of mind. I'd maintain that most of us are drunk on our egos all the time, and only occasionally achieve lucid, ego-less moments).
One of my common laments as I come down from a shroom trip is that no matter how hard I "shake" my brain up, it always seems to settle back down in familiar patterns, many of which I dislike. I can feel my ambition coming back, but so does my ability to feel insecure. Confidence along with arrogance. Diligence along with anxiety. But this is not a bad thing. When we hear about people having psychotic breaks after a psilocybin experience, that is precisely the failure of their brain to return to its old configuration. We don't actually want to lose that old structure wholesale.
So wouldn't it be amazing if we could "shake up" our brain on a shroom trip, but choose the portions of our personality that we'd like to keep, while allowing the rest to be rebuilt?
The universe, of course, allows for no such shortcuts. But this raises the question - why do you need a chemical substance to shake things up in the first place? The brain is not made of stone: you don't need acid or a jackhammer to break it down. You already rearrange your brain every time you learn something new, form a habit, or finally forgive a person.
The power of shrooms to affect depression is not mechanical, in the way that SSRIs act to temporarily change your serotonin levels. It may not even be accurate to call it a treatment. I stand by the opinion that the only person who can really treat your own depression is yourself. Good therapists, psychology frameworks, and religious traditions offer tools that can help get you there faster.
Mushrooms, safely used, can be one powerful addition to that toolkit. It is liberating to see the world from outside your own narratives, if only to realize that so much of your "reality" is actually constructed. That knowledge, remembered in the right moments, can lift the weight of emotion enough to allow for progress.