you'd think for someone who got forced into like 4 rounds of cbt over the course of my adolescence, i'd have more to offer lol. but i do agree that writing letters is a great idea. i also really love to write poetry, and i find that it's a good outlet for me, because i get to get my feelings out of my head and onto paper, but also, i have something tangible to point to and say "wow, look, see that? i made something cool." in that sense, i think art is a good coping mechanism in general.
also, when my thoughts are racing or i feel just generally misaligned/weird, i like to watch cooking stim videos and look at nostalgia pages on instagram and tumblr. but more broadly, if you like any kind of "satisfying" videos (soap-cutting, kinetic sand, slime, bread rising in the oven, etc), chances are you'll find hundreds of them just searching the tag. in general, distraction is sometimes a better coping mechanism than we're often made to believe it is. sometimes it's just impossible to take your mind off of things, and i get that, but i think a lot of people feel like they don't have the "right" to take their mind off of things, and you always do. everyone's got different tastes, but one of my favorite things to watch to distract me is kenniejd's "bad movies and a beat" videos (she's a youtuber) because they combine 2 things that hold my attention; she roasts bad movies and does her makeup, so it's like a full audiovisual experience lol.
i have this mentality (that i'm trying to shake) where i just won't let myself not feel/think things. i don't know if it's my ocd obsessions+intrusive thoughts or what, but where some people need to learn to stop repressing their feelings, i need to stop forcing myself to follow every train of thought i have and dig deep into every feeling that scares/hurts me the moment i feel it. sometimes it just isn't the time, and i need to convince myself of that. that's why sensorially stimulating things are so helpful for me, because if i'm totally engaged by something else, i can't overthink myself into oblivion :') this is so rambly but i hope it helps someone