That is just something about life.
We should try never to go back to the person who left you. People who broke your heart, people who never show you care, people who hurt your feelings, people who wasn't there when you need them most. People who never show you love but hatred, people who never lift you up but bring you down, people who never encourage you but discouraged you.
If they can leave you once when you need them most, if they can leave you when it matters most, they won't mind leaving you again the second time.