To elaborate more on what nongreenthumb said a bad trip on acid or mushrooms or any hallucinogen can really discourage you from doing them again. I've seen people end up convinced they need to go to the hospital when they're really fine and then try and convice the hospital staff that they're the Son of God and try and convince the hospital staff of the same thing. I know a guy who got in a huge fight with his wife, didn't tell my friends and I and came and tripped with us, three hours into the trip he was just sitting there, speaking only in metaphors and trying to get us to drive him to a bridge so we could watch him jump off.
I personally took a ten strip and went to schlitterbahn (a waterpark in texas) and I was pretty much crazy. The hallucinations were so strong and on so many layers that I couldn't distinguish reality from the visuals, when I closed my eyes I saw thousands of people at a waterpark, when I opened them I saw thousands of people at a waterpark only with a lot of differences between the two like rides being in different places, seeing people that I knew couldn't be there. So I tired to figure out which was the real reality for a few hours, trying to hide clues in the scenery in my mind so that I could find out what's real. Then I started to get scared that I might not actually be able to pick reality out of the basket and might be stuck in some scenario my mind created so my mind got more turgid and unclear and the sheer number of people at the waterpark was terrifying to me, and the parents walking by with their kids crying stuck out in my head, I experienced ego-death and thought that I might be dead as well and that's why the kids were crying, and it scared the shit out of me, by this time I was just laid out on a lawn chair still trying to find reality and stuck in-between a bunch of plausible ones with lots of auditory hallucinations of different people, including my parents talking to me, people saying 'You took too much' and all this replaying in a loop in my head pretty much. I managed to find my cd player near my lawnchair although I don't know how it got there, I had Dark side of the Moon in the cd player and I just sat there and listened to it, I already knew every note but I'd never experienced it like this, I can hardly explain how it felt, when the crescendos would hit I'd feel GIANT waves of euphoria and get some amazing 3d closed eye visuals, and then pieces of the lyrics started sticking out to me, as though they were there for me to derive some benefit from, the lyrics in the first song, well not really lyrics, the guy talking says:
"I've been mad for fucking years, absolutely years, been over the edge for yonks, been working me buns off for bands..."
"I've always been mad, I know I've been mad, like the
most of us...very hard to explain why you're mad, even if you're not mad..."
And then the next song ends with these lyrics:
For long you live and high you fly
But only if you ride the tide
And balanced on the biggest wave
You race towards an early grave.
When I heard them my whole body got that shiver, and then there's one part on the album where I swear someone whispers "If you can hear this you're dying" but then the album gets into more uplifting songs I suppose with Brain Damage and Eclipse, by the time the album was over I had a giant shit-eating grin on my face and I was back to just tripping balls without all the negative thoughts that scared the shit out of me, so I went on some rides and had a ton of fun. The whole reason I had a bad trip at all was because I was stupid and didn't follow one of mine and many other peoples' rules for LSD, I took it when I had a lot of things to worry about and so I focused on those rather than on having fun. All in all the trip lated about 30 hours from the ten hits, and it was one of the most enlightening and fun and scary experiences in my life.
