I've done a lot of tripping, perhaps especially for someone who's only just shy of 21 (but then I know people who were tripping way younger then me, even quite heavily, so I don't know?), my brain definitely has a permanent or at least very long lasting degree of leftover psychedelia to it.
I've also abused/overused psychedelics a ton, done some shit I'd advise others to never think about, but there were only effects I'd consider negative during those really abusive periods then for maybe a few months after (and they were never any worse then shit my head has done all alone, possibly less negative then when I was smoking pot like 10x a day too, at least behaviorally), generally speaking leftover perceptual alterations don't bother me, and the mental effects help me feel more relaxed & hold a better perspective on life.
Abusing dissociatives, however, is a different story. Using them moderately for a long time they were quite helpful, really had a special way of obliterating the minds defenses & showing you more personal/emotional things rather than the more general life stuff of psychs (not that they aren't emotionally helpful too), and dissociatives have a very special way of exposing the darkness within, but making you comfortable with it & showing you that it isn't "you" but a result of past shitty life circumstances, but then abusing them can cause you to dwell in that darkness in ways that are unhealthy, and can dig up shit you might not wanna think about.
Dissos also have negative effects on cognition which psychs don't for me. I stopped using dissos (MXE, perfect drug for me in all the worst ways) 2 months ago, my head is mostly cleared up from them, though I'm still left a bit spacier then normal & lots of sleep deprivation gets my head more scrambled from them. Good thing I was able to stop myself before it got really bad (thanks to taking a psychedelic as well the last time I did MXE, allowed me to see what MXE was doing to me more clearly).
I've had a lot of social anxiety for longer then I can remember, obsessive compulsive disorder, always been highly neurotic, and my hallucinogen use, while it hasn't eliminated those issues, has made them much easier to deal with, and made MUCH better at dealing with people, more empathetic, less judgemental. As well, until a certain point in my tripping I always had some degree of baseless anxiety under the surface, thats gone now, I only have anxiety for actual reasons (so sometimes I can reason my way out of it). I also feel that separating from my ego so much has made me more rational, as I fall for selfish/egotistical logical fallacies far less (but of course the ego is still there, even if I know it's a liar).
