Any time you allow a child to get away with a certain behavior, the message you're sending is that the behavior is OK. If there are no real consequences to his actions, all he can assume is that what he did is OK and he can get away with it.
I don't know of anything else that could have made me feel worse or more of a failure. Those words confirmed my worst fears: I am not good enough. I am not doing enough. I am not strong enough. I am not capable. I am a failure.