We begin utterly consumed by ourselves. Another major problem to being good is laziness. Goodness takes effort. That's another reason why the world is naturally tilted towards the bad, because it takes nothing to be bad. You've got to do something good or suppress something bad, to be a good person, unless you're one of those rare persons who are naturally predisposed towards being goood.
Different persons have different degrees of struggle to be good.
The third obstacle to being good is weakness. Goodness takes courage and courage is a rare quality by definition. If something comes easily to you, you don't need courage to do it. The greatest single obstacle to being good is lack of empathy. I suspect that empathy is more built in to some persons than others.