If he has done it once he'll do it again, but what if he truly changed? You want to make it work but the trust that was once intact ,is now gone. It'll take months or maybe years to trust a person who once torn your heart apart, and even then your restless mind will invade your head with insecurities you had consider buried over time. That's why trust is one of the best gifts a person could grant, it only gets to be kept once, if lost consider it gone.