I believe that our minds are much like Large Language Models. Our brains put together and combine and mix up sentences that on average have some benefit to us. We speculate to explore possible outcomes. We practice saying sentences within our heads and then explore their possible consequencees.

It is a random (but not totally random of course) process where one thought gives rise to new ones. I think that depression means being in an indirect loop of negative thoughts which amplify each other. Phychedelics might be a way to break out of such loops. But, I'm just speculating here of course.