Here's my perspective on letting go. If you "Let go" and still obsess, worry, stress, fret, panic, throw up or snoop, you haven't really let go. Letting go will feel almost like indifference; regardless of what she does, you're going to do your own thing, what's best for you and your kids. Sure you'll stress over small details, about custody arrangements and finances, but over losing your W? Nope. Let go.
I agree completely with this, but I also know, from my own experience, that you can't tell someone to let go. It has to happen at whatever pace they're capable of. I think it literally has to do with the brain slowly rewiring itself to remove the other person from consideration. It doesn't matter how much the folks here on the board say "let go" over and over, but there are things that can help the process along, particularly no or minimal contact.
Only now, after two years, do I know I've finally let go. My W sent me her proposal for our divorce yesterday, and I had no emotional reaction when I got it, other than contemplating the meaning of some of the financial numbers. Looking back, I now understand what folks here, my friends, and my family all meant when they said I still hadn't let go. Everything I did in the past was in some way a reaction to what she was doing. Not any more. I've finally let go, but I know it could only happen as fast as it did.