Why mourn for someone that can't/doesn't want to be with you?
Being loving and co-dependent at this point is not going to work.
Think back to when you first met, what was it that drew you together? What made him attracted? What changed after the relationship? What changed after Marriage?
Go back to that original you, but here is the twist....BE DIFFERENT. Do what you wanted to do, express yourself, be YOU. Go back in time and try to accept that old you, but make it even better. F him right now. You will get NO WHERE feeling the loss.
