What is wrong with this letter?

Show your letter to a clmate (old friend) and see what he or she honestly thinks. Secondly, put that letter away, get a good nights sleep or two and then re-read that letter and see how that makes you feel. Getting a good nights sleep gives you fresh perspective so when you re-read the letter, you'll read it with fresh eyes. That way you can make further changes/edits to it and by doing so, you'll THANK yourself for doing just that!