"YOUR EX IS YOUR EX FOR A REASON"
I'm a firm believer in second chances, in most situations. But if it doesn't work out the second time around, stop giving out chances, it's called a "second chance" not a "third chance" or "fourth chance" even if this person means a lot to you and you love them with everything you have, someone is always getting hurt and someone is always getting disappointed, and that right there, is not love if you continue to get hurt. So do what's best, and let go, it'll be hard but do it for your sanity and theirs, you'll find someone that will steal your heart, and that's when you'll realize that everything does happen for a reason.
(I'm sending this out to everyone because I'm going through a REALLY REALLY tough situation, but after reading this I'm slowly getting better. If you need any advice, feel free to PM me anytime.)