When people become adults, they are, of course, responsible for their own behavior. But if you look closely at someone who behaves badly, often you'll see explanations fall into place. Say, someone who's too emotionally stunted to connect that she's doing exactly what her parents did to her. Or, someone who's so afraid -- of losing people, of being wrong, of his own shadow -- that he barrels through life insisting on having everything his way, as if that will somehow prevent scary things from happening. The most despicably selfish people are often, upon close inspection, feral -- they're consumed by self-preservation, and don't have the courage to take the emotional risks that are the hallmark of civilized behavior.
Giving is a risk. Loving is a risk. Kindness is a risk. All demand that we drop our defenses; all allow the recipients of these gifts the opportunity to hurt us.