I have tripped so many times that I wouldn't even try to guess how many. I haven't had a single one that was entirely without some negative element. There are only two that were almost entirely negative.
The first one was pretty much unavoidable. A long long time ago, far far away I grew my own shrooms and was uneducated on how fungi absorb the toxins out of their environment. To make a long story short, I ate somewhere around 3.5g accompanied by moderately severe food poisoning. I spent about three hours becoming intimate with the rim of a toilet while tripping balls. It got bad enough that I spent a considerable amount of time contemplating suicide.
The second time was on an Ayahuasca retreat. I started tripping about 15 minutes after drinking the vile concoction. I thoroughly enjoyed the first 15 minutes and then the purge came almost concurrently with the icaros (singing that to me sounded like a dying animal). I didn't hold it back. But then I continued to heave until nothing more would come out. I put the bucket down and tried to focus on the trip, but couldn't shake the nausea that was soon followed by vertigo, intense fever and gut pain. The trip was still building and the physical discomfort took me to a very dark place. I literally thought I was dying. The building that we were all tripping in was filled with the sounds of vomiting, dry heaving, moaning, and the dying animal otherwise known as a shaman. I was in a place of extreme suffering, a hell if you will. At a few points that night, I thought that I might be experiencing permanent brain damage. This lasted for a few hours before I began to recover/sober up.
Other than that, when I experience "bad trips", it's usually brief periods during the trip where I feel a sinking feeling in my stomach or my thoughts begin to wander into bad places of self doubt, self hatred, depression, or just dark feelings. It's not usually a big deal, but it's always right around the corner. It's normally fairly easy to pull myself out of it. I have never felt any fear or negativity from hallucinations or felt presences. The worst hallucination I ever had was a couple gremlins hanging off the roof pointing at me and laughing. I felt like I was supposed to fear them, but I just laughed right along with them.
So on another note, there is another member on the Nexus (RabidLabMouse) that has also NEVER had even a negative element of a trip. On her last Ayahuasca session in the jungle, she describes the after effect as survivors guilt. Everyone was requesting that they make it extra strong and they did... Everyone but her was completely freaking out and loosing their shit but she had one more pleasant trip.
ghrue, I would ask you to look at this thread and see if you can find anything in common:
https://www.dmt-nexus.me/forum/default.aspx?g=posts&t=74492She is my partner for life (I hope) and I know that there is something different/special about her. If the two of you have something in common that causes this, it might help in uncovering whatever it is. I can speculate all day, but the knowledge would at the least help the two of you understand yourselves better but possibly save your lives in special circumstances or even uncover the trick to eliminating bad trips.