There are no heroes on Lost, only varying degrees of ethical and moral integrity.

Jack, just like many of the other Losties, is an antihero.

Jack will largely do what is the overall moral and just thing, but will not reclaim his former title of leader and "reluctant hero" until it is shoved down his ever loving throat, with him kicking and screaming the entire time.

He spent too much time at the start taking care of everyone and everything and had to ignore his skeletons. Well, he's finally had some quality feel sorry time and is relishing in some self-misery with his new self-misery gal pal.

He'll step back up to the plate, eventually, but relunctantly.