Really confused about this all?

My ex and I broke up about a year ago in late April. Last June I met someone and we have been together for a year now. My ex and I are still good friends, but it seems like all of the time he brings up about how he misses me and regrets losing me. The main reason we couldn't work out was the distance. I didn't mind at the time but distance bothered him so he broke up with me. Now he keeps telling me he wishes he could take it all back. We go through this every time , we will talk for a while he'll bring up old feelings and then we stop talking for a while, and then when we get in touch again it's like history repeats itself and we're back to where we started. He has somebody now and I do too, which is why I don't understand why he's still going on about it. I'm really confused about what to do or think about all of this. I told him we should let it go, we both have someone, and if it was meant to be it would have by now, but he's still upset about it and I'm not sure how to cheer him up. He has to let go sometime, why is it so hard? Any suggestions would be great. Thank you.