When someone feels relief from ending their relationship, is it even possible to get them back? I know I'll come out a stronger and better person, but no less heartbroken.
It's a feeling, and feelings change. How do you feel as you are eating an entire chocolate cake? How do you feel after having eaten an entire chocolate cake? Feelings change with time.
The only thing that wont change is that he will not want to come back to the exact same marriage that you had before. For it to be different, YOU have to be different.