So I (M29) tripped on acid for the first time last year, and it was absolutely beautiful and one of the best experiences of my life. 
But at the same time, the whole time I felt like the whole trip could turn very, very dark anytime. It was like all the good emotions and thoughts were there, but I could just feel the darkness inside me lingering and waiting to devour me, which scared me a bit.
Fortunately, I tripped in a very safe setting; I was surrounded by very good friends, we were alone at beautiful hill with no one else and I made sure that I was feeling well before the trip.

Anyone have similar experiences?