I know the feeling thinking that since your trips are going so well, it can't be possible to even have a bad trip. But bad trips are as equally bad as trips can be wonderful if that makes sense? They can also flip incredibly quickly and if you don't know what to do/can't change what you're thinking about quickly, they settle in HARD. Combined with time dilation and it's an absolute nightmare.
I haven't had a positive trip since August. It started when I was on nos and it went from wah wah wahs to high pitch squealing to a banshee coming at me. The surround was black and white swirling inwards made from the words "SCREAMING". We were in a tent so the trip made the air look like denser fluids and my friends were holding up their hands 'swimming'/feeling through the fluid but they were doing it in time and it felt like they were possessed. This wasn't too bad, in fact it was part of one of my better trips and we went on to see the rest of the festival.
The next time we tripped together though was the single worst. They came up tripping 20 minutes ahead of me and everything that happened to me, happened to them 20 minutes previous. They then guided me through what would happen, but I was convinced they were trying to kill me. My thoughts almost became facts when one of them said 'MrPorter come with me' so I did, to the toilet, he locked the door and sat down on the floor, looked to me and said "here's the bleach". What was probably an hour later he handed me a jar of water (we were incapable of washing cups) but I was convinced it was bleach and I can't smell so had no way of telling if it was or wasnt. The other friend was also having a weird trip and blurted out 'have you ever thought about stabbing yourself and ending it all?' it's a disturbing thing to say anyway so while tripping freaked me out more. I decided that was it and wanted out so I walked home, at 2am on a saturday night.
Maybe I imagined it, but I was convinced they had said something like "if he goes that way he'll get beaten up", which could only mean that walking along the road instead of the darkest dingiest path known to man was my only option. This was fine until I had to either walk along a busy road with no pavement or lights, or miles along a lit path which passes by clubs. Only one option then - road it is. Got halfway along where there was no light at all, walking towards the path of oncoming vehicles but obviously on the side of the road. The clouds transformed into my friend stabbing himself, but like a gif. Never quite actually stabbing himself, everytime I looked back it restarted itself. I managed to get this imagery out of my head and continued. A car came, beams on full lit up my world. I was consumed by the light, time dilation came into play, I froze in this wide expanding light engulfed by it. I thought this is it, I've been hit, I'm dead. It felt like hours I was in this light completely still. Eventually I came out of it and decided immediately that I couldn't continue because I was only 1/4 of the way along this road and more cars were bound to come. So I turned back, managed to wave down a taxi. The driver was a caveman wtf (he was Indian) and looked incredibly evil. I couldn't bear facing forward travelling at the speed of light, nor could I close my eyes, nor look at him so I switched rapidly. Made it home. Paid £20 for a £4 taxi and ran inside.
Took 3mg of Etizolam (no tolerance, just wanted out asap - 1mg works fine for me when stimmed off my face) and chucked all my drugs in a box with a combo padlock (4 digits),changed the combo to something random and just lay on my floor. Must have been like 5 minutes but it felt like forever before I passed out. Luckily nothing ever came of it, my brother saw me and just thought I was incredibly drunk, maybe he sensed otherwise but it didnt worry at the time because in those 5 minutes waiting to pass out, time dilation kicked in again big time and I just kept thinking 'maybe another etiz will send me off'. Lucky I knew to set a random combo or I probably would have ended up ODing.
Moral of the story kids, bad trips can come when you're not expecting it. I've had a couple of difficult experiences where I've learnt stuff and one uncomfortable one where every single visual was either a cartoon gif/demotivational pic from the internet or an inspiration to just go and do something. It taught me that I love chemistry more than anything I've ever wanted to do but it also felt like the internet had brainwashed me since I spent so much time on it.
I've laid off the psychedelics and weed since then pretty much.