The only drug that has ever given me a negative trip is DXM, which is arguably not even a psychedelic - I have had moments on DXM where I have been lost in my head, thinking only negative thoughts, for what seems like hours. In my experience, the best way to change the direction of such a trip (as others have said) is to change the setting. If the lights are off, turn them on. Light some candles. Change the music. Get up and move around. Start dancing. Play a song like "Don't Worry, Be Happy" by Bobby McFerrin. Intentional change of set is helpful as well, though it can take a fair bit of resolve to tell yourself "Ok, STOP. I'm on drugs right now. I will deal with these feelings AFTER I come down."
Don't think "If I don't stop thinking this way, things will go sour." Instead, think "When I DO stop thinking this way and start enjoying the positive things, this trip is going to be amazing!"
Don't really know about a bad trip on classical psychedelics - Both LSD and psilocybin mushrooms, the few times I've taken them, have always treated me extremely well.
Don't think "If I don't stop thinking this way, things will go sour." Instead, think "When I DO stop thinking this way and start enjoying the positive things, this trip is going to be amazing!"
Don't really know about a bad trip on classical psychedelics - Both LSD and psilocybin mushrooms, the few times I've taken them, have always treated me extremely well.