It had been a couple years since my last trip so I decided to take a whole eighth (every other time I had just taken half). I started feeling the effects much sooner than I had expected, maybe fifteen minutes. First everything seemed really funny, then the visuals start and things alternate between blankly staring at something (mostly the ceiling) and laughing like a crazy person. The loss of short term memory was a big one for me, and was probably the biggest factor in this being a bad trip. I couldn't remember the simplest things. Like the rules to being a living creature was beyond me. I kept asking my friend if she knew what food was, just to prove to myself that this wasn't my only existence. The ideas of LIFE and PERSPECTIVE became illusions. I started to become part of this swirling madness that was the universe and I thought I would keep being thrown from one existence to another. I remember thinking that it's why people kill themselves, just to see if there really is an end to the swirling madness. I regained my sense of self and gave my friend a bracelet I was wearing and gave her strict instructions not to ever take it off, thinking that it would be enough to recognize each other if the swirling madness ever brought us back together again.
Basically it scared the shit out of me. A month later and certain phrases or situations set me off into a philosophical quagmire.
All of my other experiences with mushrooms had been utterly fantastic, so in no way do I want to dissuade people from trying them. The first time is probably the best because you don't really know what to expect, and I don't advise using it if you aren't comfortable with who you are, because, like LSD, it tears down your ego like it was made out of origami paper.