Rabbi Moses ben Maimon—known as the Rambam or Maimonides—was not one to mince with words. In his "Laws of Repentance," he lays it out straight: You can be whatever you choose to be.
As liberating as that may sound at first, the Rambam makes it clear that there is also a burden attached to this truth. There are no escape clauses to your responsibility for who you are. If you are weak or inconsistent in being the mensch you are meant to be, you have no one to blame but yourself. It is all a matter of your choice. Don't let anyone—least of all, yourself—convince you that it is not in your power to be a righteous person.
The Rambam did not know about genetics, but he would not have let that be an excuse for bad behavior. Our faults lie not in our genes, but in ourselves. The Rambam understood that not everyone has the benefit of a good upbringing. In the end, though, that is no excuse, either. You cannot blame your parents or your circumstances forever for the choices you make.
I re-read the Rambam's chapters on how to make t'shuvah at this time of year each year, and it is this passage that stuns me every time. I realize that, in my efforts to be self-forgiving for my faults (and I've got plenty), I sometimes use my human imperfections as an excuse. It's not that I don't try hard enough to be good. Rather, the problem is that I put so much energy into avoiding the things I know are right.
I think this is a tendency most of us share. We all know how we ought to behave—to forgive and be giving to others, to take responsibility for our mistakes and to apologize, to be modest in accepting praise and gracious in accepting criticism—yet we end up doing whatever we can to avoid these behaviors.
It is important to forgive ourselves for our faults. None of us is perfect. But, come on already, do we really need to try so hard not to do what is right? In the end, aren't we just undermining our own happiness by avoiding the things that make life meaningful? Who wants to be stupid, cruel and miserable?
It is all a matter of choice. It is in your power to be as righteous as Moses. Don't let anyone tell you it isn't so.