Yeah I think "bad trips" don't really exist most of the time. Tripping is not like flipping a coin and getting "good" or "bad". It's like normal life in the way that it can be anything in between. It has good elements and bad elements. I don't have much experience with drugs, but I know that I never had a completely bad experience. A few weeks ago, I had my most intense "trip" (I call it that because it was very intense, even if it was just with weed and alcohol).
After smoking and drinking, I'm sitting on the sidewalk with my friend and then

I realize that I must have fallen asleep or passed out because I am certain that I'm dreaming, everything feels unreal to me. I feel a bit panicked at first, but panic transforms into some kind of "fun fear" (like when you go on amusement rides and you are a bit afraid but you laugh and have lots of fun because you enjoy the feeling and you know nothing can hurt you). My friend starts to walk away and I feel like if he goes too far from me and I forget that he exists, I will completely leave reality so I yell "hey come back here, please stay close to me, you are what keeps me attached to reality". We spent the night walking around town, with me kind of freaking out but enjoying everything. When my friend was too far from me it was really scary and I wanted to cry, but as soon as he was close to me I felt safe. I saw stuff that was frightening or that made no sense (everything had a weird appearance, like some stuff on the ground that took the form of a big frog or dead bird parts, or the people around us that all looked like they were dressed strange) but I just thought about everything as some big video game so I could face it all.
We can't say that I had an entirely "good" or "bad" trip because there was both positive (like the fun sensations) and negative stuff (like the scary things). It's just a trip, with all this stuff combined. One thing that helps to avoid having too much negative stuff is to learn to laugh at the bad parts, stay positive and remember that your perceptions are altered.
Man this was difficult to write! If it sounds like gibberish it's because I haven't written in English in a long time and also because I had trouble finding words to describe an experience that was so unreal. good luck reading