Not sure it's a boundary violation but I was really angry with my first t years ago because she unavoidably had to cancel my session and there was no other space she could offer. I wrote her a letter saying I was going to kill myself and sent it just before my next session, by which time my anger had died down and I felt really ashamed. Poor T was left not knowing if I'd turn up or not or what to do. She'd only just recieved my letter for various reasons so all she could do was wait and see if I'd show before taking any action. It was very distressing for us both and I would never do it again. Fortunately I have grown up a lot since then.