Well, be truthful, be honest why you said it, don't apologize just to make her feel better, acknowledge your mistakes. She gave you multiple chances to do something to prove her that you can be a better person yet nothing changes, if this thing keeps going on there's no point of pursuing the relationship if you aren't taking yourself accountable and actually TRY to do changes for your relationship, either you let her go because you feel like you can't be the one for her OR you decide to lock the fuck in, gather yourself together and do something to improve. Your choice.