I am sorry you had such a low night, but it sounds like you are starting to accept some things that I know, from experience, are very hard to accept. After my H gave me the "I am done" speech back in May, I went through a week of mourning my marriage. It was a really low point, but I had to go through it. I can definitely say that, from that point to now, I have grown stronger and stronger. This is just part of the process for you. You have to allow yourself to go through it, but you are right, you are going to be fine. In fact, you are going to be great!
