I do know a few couples who broke up, moved on with their lives, but then got back together and happily married. In these cases, one person (usually the man) had a come-to-jesus maturity awakening, and sincerely changed, and the other was in absolute shock before giving a second chance.

And...I've known many couples that kept breaking up and getting back together.

I once reached out to one ex, because I didn't like how we broke up at the end, and I wanted to give us another chance. She never wrote me back. :)

I've had two or three ex's reach out to me, and in each case we at least started talking, but it didn't work out. Either the same issues were starting to resurface, or one/both of us changed enough that we no longer could connect.