Broken Promises

They said promises are meant to be broken
others said if it is broken it is not a promise.
He was promised me that he won't leave me
what ever happens. I did believe his promised
but he broke his own promise just because he
found someone better? I once did asked myself
what was wrong with me. The promise that he
made were not even fullfilled.

I let him go. Then suddenly, One day he came back
and told me I should give him another chance and he will fullfill his broken promise. Should I give him second chance? Does he even deserved it? How can I even make sure that he can fullfill his promise? Is it even worth it to give him another chance?