I've had mixed results, and used quite a few hallucinogens over my younger years. Will break it down by the two major (only ones I had bad trips on). I also had good experiences on both acid and shrooms, but the bad ones turned me off in the end and never went back to it.
Shrooms - Beach week my senior year. Got a couple ounces of shrooms and headed to SC with some people. Had to ride out all night to go get them from my friends frat brother at a college 3 hours away, then head back to home town, before departing for a 6 hour ride to the beach house in SC from VA. So, being up for about 2 days, I decided to have about 6-8 20mg of adderroll to start the journey. When we got to the house, everyone passed out (of course I couldn't sleep) and proceeded to pull caps out of my shroom stock. Ye of little patience kept eating, not knowing how potent they were, and got to about 8 grams when all said and done.
Shrooms are wonky to begin with, kinda dark, grimey trip... But this hit like a ton of bricks. Visuals out the ass. Rooms expanding forever and back down to tiny. Couldn't talk, swallowing was hard, mind racing all over the place, couldn't walk (maybe just was too fucked up to), but when I tried it was like I was drunk as hell. Swore I was going to die. Felt like I was slipping away into nothingness. Trips only supposed to go 4 hours or so, but this lasted way longer (probably mixing it with the addies in high quantities, staying up for 2 days, and the dosage of shrooms).
When I came out of it, I cried for hours. I wasn't right for a while. I can't really explain it. When I tried to talk nothing would come out but tears. Couldn't verbalize anything when I was back into a safe place in my mind. Was a really really crazy dark trip that changed my perception on death for the long haul. Swore i was going to die.
On to LSD - After those shrooms I swore off of them, but decided I'd get some paper from this traveling Hippie dude with a fresh stock from a New Years PHISH show he brought back. Damn paper dragons. Took them up to a friends in the mountains and we both took a couple tabs. That shit set on like a bat out of hell. It was good, real good, like I got shot out of the pleasure cannon. Problem is, I kept going up... wouldn't stop going up. Got to be too good. Mind was gone. Periods of time I couldn't remember who "I" was. Lost touch with my inner monologue. Sensory overload. They put on some jazz music and my eyes started rolling in the back of my head. Just couldn't take the intense feeling. Felt like I couldn't remember how to breathe. My friends walking circles around me bc he says when he sits still shit is too much to handle. Felt like he walked circles behind me for days. Tried to go to the bathroom and literally forgot how to pee I was so fucked up. Damn trip went on for about 10 hours. Just too much. Didn't mess me up emotionally or mentally like the mushrooms, but I'm sure the anxiety I had this trip correlated with the bad trip on the mushrooms.
Ever since those two I swore off. My brain and emotions didn't mix with them like they had previously on my good ones. The good ones are amazing, but the bad ones are just as bad on the opposite end of the spectrum.