revscat23 and EE briefly mentioned this in their writeups, but I thought I should expand on it slightly.
A trip is strongly influenced by the subconscious. A happy state of mind usually equates to a good trip. If you're sad you're likely to have a bad trip. In the more extreme case of self-loathing you'd be almost guaranteed to have a horrific trip. It's for this reason that I'd advise for people who suffer from depression, and severe self-hatred to be very careful, or stay clear of hallucinogenic drugs altogether. Any trip can be a dangerous ride into the subconscious and can have damaging psychological consequences.
- Just a friendly warning from someone who cares.