joss, It's not you...it's him. You have to retrain your brain so that you can remember he's not the man you married. He's going to be the exact opposite of that person, i.e., mirror image. He's going to act like a teenager, say things that are off the wall and his behavior is going to be that of someone you wouldn't want to have around. In fact, your children will be more mature than he is.
Keep the expectations at zero because he'll say he's going to do something and then he won't.
Hang in there!
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
