I've written my goodbye letters to everyone 1000x over in my head
Why are you constantly thinking about goodbye letters?
I think I also imagine having to detonate a bomb at a Warhol exhibit.
Is this fiction or something you're actually planning? You can seriously hurt yourself and others, and if you are planning on committing suicide, just know that you can get help from me and other professional therapist.
I would never do such a thing, these are just my letters to everyone.
Even so, I feel like you're being dangerous by thinking about committing suicide and bombing a place, as there's still a slight chance that you may act on it in the future. If you really want to just send letters, try to just go send them sincere and honest letters, instead of thinking about dangerous plans.