We were so tied together, it is hard to let that go!
Absolutely, it is really hard. One of the hardest things you may ever have to go through. It's a bumpy ride but things will get better.
I understand your feelings of desperation, and those aren't going to change overnight. Eventually they will.
Letters never work, and I mean NEVER, in these situations. Journal your feelings, post them here if you need to, but if you ever feel the urge to deliver a letter please please please fight the urge and post here first.
