Move On and Shut Up

While sitting at my computer and looking at facebook and other social networking sites, I see peoples views about the past. I wonder if all you can talk about is the past, then why did you leave it, why did you change the way things were? I had a boyfriend/fiance for 5 years and I don't talk to him nor do I talk to anyone in his family. When we broke up that was it, we haven't spoke since. I left him in the past. I just can't understand how people can be so hung up on the past, clinging to every memory they had. Sure I have plenty of memories from my childhood and high school, but they don't include my ex. I've moved on in my life, got married and I'm making new memories with Grant. I don't sit around and think about things that happened with my ex. I do miss some of the friends and (his) family I lost when we went our separate ways, but I knew that was a loss I was going to endure. We (past friends and family) were around eachother almost everyday so we all became very close, so I can't understand how people who barely saw eachother can still, especially againts others wishes, keep in contact....loneliness is the only thing I can think of.
If all you think about is the past, how can you move on?

"Stop acting as if life is a rehearsal. Love this day as if it were your last. The past is over and gone. The future is not guaranteed." -Wayne Dyer