If one was convinced that the pursuit of happiness is the highest priority in human behavior, it would be easy to ascribe every strange behavior to a strange sense of happiness. “She likes to tear her own wounds open.” — “Well, probably, for her happiness is to be bleeding and in pain.”
Nevertheless, except if one defines happiness in a way which has absolutely nothing to do with brain states and it’s pleasure centers, people are always doing things that are not likely to enhance (or even maintain) their overall level of happiness. The girl who insists in letting herself be used by a boy who will certainly leave her in the worst possible terms afterwards, over and over again. The person who gets the job that will make him miserable 90% of the time but has a 20% better payment. And so on.
In my personal experience, if you pick a random situation and make an evaluation of which behavior is more likely to generate the most joy to a person, most of the time this behavior is rarely opposed to the one the person actually displays, but never exactly the same. That is, although people generally can be said to act in ways that avoid making them miserable, they cannot be said to act in ways that maximize their happiness.