Well this hits too close to home. I think I know how you felt, I also often feel like I could have done more once the situation has already passed.
But trying to righten your mistakes is, I think, much more important than trying to never make one. Because we are all humans and we all sometimes do things we are not proud off. But trying to be a better person next time already makes you a great person; not many people would bother or even understand that.