As I learned a long time ago, once it's over, it's over...if she didn't want to move on she would have made every rationalization in the book to stay. But as it turns out, that was not the case. Unless she's visibly flirting or hinting around, it sounds like she sees you as a friend now, and as many experienced guys will tell you, you don't easily get out of "friend zone" once you're her buddy.
Would a salesman be spending better time going after someone who won't give them the time of day, or someone who shows a hint of interest in what they're selling? Exactly the same here. There are more women out there - and one of them might be dying for a little flirt or attention from you. You admit to your faults which lead to the first relationship dissolving, now take that knowledge to better yourself and sweep someone new off their feet. ;)