If writing the letter were going to be completely easy for you there wouldn't have been much point in doing it in the first place. I figure it's the process of writing it that's important, more than the finished product. Keep hanging out with it and noticing what comes up for you.

A lot of the things you were going to say in the letter you've already discussed with us here, haven't you? You may find that they're all still true for you but you're now encountering some barrier(s) that you'll need to get past in order to say them. Or you may find that something different is true for you now, or that you're not ready to say anything at all yet. I'd recommend (you probably already knew this) that you take what you get.