Most of us tend to give chances to people specially when they have a huge part in our lives. In my case, I do the same. I don't have any problems with that. There will always be an instances that we were consumed with the thought of "changes". We believe that they can still change for you. That they will be able to fulfill their words this time. But on the contrary, second chances should only happen once. This won't be called "second chance" if you easily gave it to a single person "ten times".
We give chance hoping that we could fix things this time, but if they tend to repeat the same mistake again, then start walking away. Because the more you give them chances the more they will think it's so easy to hurt you because people will get use that you'll forgive them easily too. Until the repeated mistake will became their habit.
And if they waste the chance that you've given, remember that you aren't a narcissist for building your walls too high, not giving them any access to your life, once more. You aren't a self-centered person for saving yourself after the betrayal they offered, when you do nothing but accept and welcome them.
You aren't a doormat where they will comeback when they want, say sorry when it's convenient for then repeat the same mistake again. Careful on what you tolerate because you sometimes, you're the one teaching people on how they treat you. Don't make them think that the habitual doing of mistakes and disappointing you is fine just because they mattered to you so much.
Again I will say, "second chances shall happen the way it is, and not freely given ten times"