1000 micrograms of acid when I was in my early twenties chased with weed. It was the most unequivocally awful experience of my life and the significant consequences of the decision lasted years (panic attack, tracers, visual symptoms, insomnia) and required psychiatric treatment. The symptoms actually responded really well to clonazepam, but discovering that treatment took a very unfortunately long amount of time because of the obscurity and stigma of a diagnosis like HPPD. As well as the stigma of benzodiazepines themselves of course. Coming off the clonazepam later on would also be its own special hell. I'm fortunate to have ultimately emerged from that situation with only very mild long term effects (a little slightly moving text when I'm tired), but that decision fundamentally changed me and almost drove me to suicide.

Weirdly, after those negative symptoms subsided I found that my nearly lifelong case of OCD was almost completely gone, perhaps because I had just fallen so fundamentally out of the habit of indulging my compulsions as they did absolutely nothing to decrease my anxiety during that time period. Or perhaps it was directly the effects of the acid itself. I couldn't say.

I've made many many bad choices that compromised my safety and sanity, but that one really takes the cake because of how assaulting to my very sense of self it was. It was through that experience that I really understood that the idea that young people have a sense of invulnerability that colors their choices is not just a cliche or amisremembering of older people. It's very real and it was an illusion that was violently ripped from me in the most painful way possible. I'm a much more careful person now and, in a way, much more existentially interested in death and what it says about our lives.