About two years ago I was going through an intense depressive episode, over several things going on in my life (mostly social isolation, but also some family stuff). My two best friends knew I was down but I didn't tell them just how much I was struggling until it was too late. I was experiencing intense loneliness and became paranoid at losing the friendship. I became emotionally unstable and demanding of my friends. What I am most ashamed of is that I accused them of conspiring to exclude me which obviously broke their trust.
I'm now doing a lot better, and have an active social life. But I still miss them and think about them. About 10months ago, I sent a message saying I'm sorry for how I acted when I wasn't doing well, that I'm doing better now and that I want to reconnect. This message came after several months of distance (I asked to meet a few times, they didn't want to). They both said they do not want to/don't have the capacity to rekindle the friendship. I thanked them for being honest, no hard feelings and said I wouldn't contact them again.
I've really been thinking a lot lately about how wrongly I acted and how much I hurt them. I wrote a more detailed apology (about two pages) taking full responsibility for the things I said and did without any excuses about how I was feeling, and instead only focusing on how I affected them. There is nothing in the letter asking them to change their mind on the friendship.
I wish they understood just how truly sorry I am and how much I regret everything. I feel my original apology didn't fully convey this. These two friendships were very meaningful to me (they were my closest ever friends up to that point). I don't want to leave this unsaid as I realize now how much I hurt them.
I recognize they already ended the friendship and I did say I wouldn't reach out. Would sending my apology letter (via text or email) be respectful or would it be crossing a boundary? I think if the roles were reversed, I would like receiving a letter as an acknowledgement but I realize some people wouldn't. I really don't know how they'd feel about it or how they feel about me now. If I do send the letter, how do I do so?
I am especially interested from hearing perspectives of people who have been in the same situation as my friends.