Why do ex's always come back once you start to move on?

After 6.5 years she breaks up with me, and three months later she is trying to talk/text me. It seems like it's always three months after people break up they start to show some interests in getting back together after you begged and told them how much you love them. Anyone else have this happen to them?
Why do ex's always come back once you start to move on?
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