I'm just a single kid, so I don't have my own family and know what marital problems or problems with children are like, but in my situation, I don't think there is a worse kind of pain than breaking up with someone. It just kind of rips your heart out, almost like a piece of you is being surgically removed with a dull, rusty, hedge trimmer. And I wish there were a better answer than just time, but I always think that's the only thing that really softens those wounds. Fresh memories and experiences are raw and they hurt, but time and experience has a way of putting some distance between the pain of the past and allows us to recover and move on.
After Becca, it used to be that I couldn't listen to this song without feeling all of those old wounds open up again. I can still remember the morning she came over and we were sitting on my couch, listening to this song, and she told me that she had never been happier than in that moment, and I wanted more than anything to freeze that moment in time so that we could always have it together, but things didn't work out. This is the neat thing about moving on - the salience of the memories that you have tied to the triggers, whether they be songs, places, smells, etc. become dulled as you receive continued exposure to those things and the trigger draws new associations with other things.
This is a shortened version of my advice on moving on: cut all ties, allow yourself to mourn, but don't dwell or wallow in the past, and look for new relationships, not replacement ones. You know what really surprised me? Just how good the advice is in this WikiHow article about breaking up.
You know what's a nice part about breaking up? Life moves on. One way or another you're going to wake up tomorrow, the sun will rise, and you have another opportunity for a new start. Getting to know new people is a good thing. Forming new relationships is a good thing. And having another opportunity to get things right is the best thing.