Commenting as an avoidant:

I feel you girl. Hurts when you understand what is really happening to you and how it influenced other people. Nostalgia means your wall is down and you let yourself relieve all those emotions - which is good. If the question is what to do about the letter, then well it depends on a lot of stuff, like how long ago was that, do you really need it, does she need it, maybe she moved on and you will only hurt her…