This too is what we are.

Sometimes we behave in ways we never thought possible. We manage to be polite to somebody we really hate. We are rude to somebody we respect. We fight with people we love. We do things we didn't think we could or things we wish we hadn't. But is all us. Single entity. One.
Do we hate ourselves for the wrong we do? Is regret a solution to anything? We need to accept our mistakes, as a part of our person. My mistake. My fault. I'm sorry. It won't happen again. And if you really do regret, it wouldn't happen again.
But sometimes we repeat mistakes. And we never forgive ourselves for it. Forgiveness is not something that comes from outside. We are forgiven, when we forgive. Others. Ourselves.

Like Salman Rushdie said in his novel The Moor's Last Sigh:
"When a mistake of the heart is revealed as folly, we think of ourselves as fools, and ask our near-and-dear why they failed to save us from ourslves. But that is an enemy against whom no-one can defend us."