I understand your feelings as I am currently in the letting go stage, too. For the second time. Mine sobered up after I let him go back in 2005, so we decided to try again. Sadly, it hasn't worked and I have to let go again. It does suck. And it is the hardest thing I've ever done.
FWIW, I don't think it's letting go of the person that's hard. It's letting go of the person I hoped he was or would become. And all those dreams and plans I had for the future. It's extremely painful.
But, there is a silver lining. I get to create new dreams and plans. And I'm smarter now. I won't make them dependent on someone else. I create my own life from now on. That's very exciting.
Give yourself some time and don't feel bad for feeling bad. It's natural to mourn the loss of an important relationship. After a while you will have more good days than bad. Unfortunately, you have to go through the pain to get there. (((())))
L