what is it inside our heads that makes us do the opposite?

unlike physical pain, which i learn to avoid very well, quite often without having to first experience it, i'm pretty bad at avoiding emotional anguish. in fact, it seems like i actively seek it out. i feel so stupid for picking at old wounds, for letting myself lapse into the same pattern of thinking that has made these past few months so miserable. what i am getting in return for this misery can't be worth it, but nonetheless i'm all too ready to pay the cost. am i irrational then, or is there something i'm missing?