My friend had a severe psychotic snap in 2017 that destroyed both of our lives when I functioned as a live-in caretaker for them for a few months in another country (what was a shorter Xmas vacation extended into February.)

While it was of course an awful time for my friend, it was also a hellish year for me. Because it impacted my life so intensely, we laid some ground rules where they had to talk to me before they thought about smoking weed again. They professed no interest ever again to ease my fear (I would even call it a phobia.) Things were okay from early 2018 to this year.
After agreeing that they'd always talk to me first so we could talk about the dangers and pros/cons, including my personal wounds from last time and the risk to my own mental and emotional health, this year, my friend snuck weed and smoked without talking to me about it first. The way I found out was in the middle of a voice chat, they hit their pipe and didn't mute, so I heard the bubbling and asked about it pointedly.

They acted mischievously about it, like it was a joke or they were being cheeky by doing it. I was really hurt. I mentioned simply that I felt concerned for their mental state, and mentioned that I thought we had an understanding that it was a very traumatic thing for me to go through, and it wasn't fun to be dragged through another completely avoidable roller coaster experience. They know me, they know I'll stick it out, so they did it without worry of ultimatum.

It sucks on a lot of levels.

So, as expected, them smoking triggered another psychotic episode. They go between seeming okay and cogent, to difficult to understand and confused. I can tell it's about to get really bad; they are right on the cusp.
I've been as calming and simplistic and minimal as I can about stuff. The roller coaster is starting, so there's nothing I can say now other than staying minimalist and unconcerned, supportive and humanizing (because it's easy for people to helicopter, and I really don't ever want to control freak them when they're an adult who deserves autonomy and respect.)

My caretaker trauma/ptsd came back really bad. It builds up like a pressure in the chest and head.
I'm really disappointed and frustrated in my friend. I am being calm and supportive tonally; after the last time I know what not to do, so I am the perfect trained caretaker for their experiments, I guess. The first time they had a psychotic episode, the doctor said the next time was potentially permanent, and we have no way of knowing. So my friend took this risk even knowing these stakes, and they did it in a way to hide it from me. I have never once challenged their autonomy or their right to do whatever they want. I merely thought we had a mutual respectful understanding and agreement about the risks and they sure did talk about feeling honorable and focused on the goal a lot.

I am trying to hold it together. I know (I hope, merely based on the first time) that the psychosis is going to eventually ebb away again, but it's just so painful and traumatic to go through all over again because of their choices. The fact they hid it makes me feel like I'm expected to be a parent or something, like if they just said "hey I'm gonna smoke up" I'd just say "Okay, be careful and let me know if you feel off, also try to keep to a low amount to start." There was no fucking reason to hide it like I was going to ground them if I found out, and it made me feel so... don't even have a word for it. Help. lol
I think a lot of trust was damaged this year on a lot of fronts.