Imagine the following situation: There's something that bothers you, something that hurts you for a long time, and you repeat it in your head, over and over and over and over and over and over and....getting quite tiresome, isn't it? And you cannot seem to let it all go, you just are not able to let your feelings come to a rest, nor yourself.
The only one who seems to be making some sense is your mind that tells you to just "Effing let it go already!!!". And yes, at some point, you should just listen to it, for a change! What is the use of chewing all the old stuff over and over again? Despite all the "But it still isn't fair that" and whatnot, if it helps you lead a normal life again it's worth it!
Love,
Andy