Eh, I won't beat myself over it. It's a useful step in helping you to move on. Our brains are wired to seek closure, so sending that letter, however cringe it may be, will help you see the reality and finally close that chapter in your life. Had you not do it, your brain may still be stuck with all those "What ifs" scenarios. Now that you're a little wiser, I hope you won't repeat the same mistakes again