I had this on alcohol + an unhealthy dose of psilocybin, apart from the difference where the only thing I could think was "I don't even know what 'exist' means". Scary but luckily I had some close friends that were comforting me throughout the experience.

For the most part though, my small experiments (LSD, mushrooms, DMT) have had a very positive and borderline revolutional effect on my outlook on life. Only time I've had negative experiences have been on mushrooms, both LSD and DMT have always been positive.