I've never had a problem controlling my thoughts on any hallucinogen. There's always that thing in the back of my mind telling me it's just a drug. Perhaps it's just that some people have a predisposition to losing it. I have had one bad trip where I believed demons were coming out of the walls and chasing me, but I was fine less than 3 hours later.
Peyote is the only drug that has gotten me so far out there that I couldn't hear the little voice, but it wasn't an unpleasant experience and I had a good sitter. I have yet to try DMT but I hear that's a hell of a thing.
I just think you have to go into it all with the idea that everything is going to be fine and make sure the setting you are in is suitable for the experience and your mental state is sound.