I'm not sure how to answer that question. An affective state that one tends to want more of, but that doesn't distinguish it from some other such states. The thing that is (or at least feels like it is) common between, e.g., the following experiences:

• Having nearly finished eating a very tasty and large, but not too large, meal.
• Confidently anticipating a promotion at work.
• Successfully finding a solution to a difficult mathematical problem.
• Playing with one's children.
• Sitting companionably with friends.
• Having just been unexpectedly kissed by someone one has long admired and desired.
• Being on an exhilarating but not actually frightening or nauseating roller coaster.
• Religious conversion (if ecstatic) or deconversion (if a relief).
• Learning that one does not after all have a life-threatening medical condition.

(I could prolong the list considerably, but I don't think it would add much. The items in the list are all "self-regarding" in some sense, but for most people plenty of "other-regarding" things could go in such a list too.) What is (or feels like it is) common between pleasure, satisfaction, and joy. (But those terms are doubtless in as much need of definition as "happiness".) One's instinctual sense of the extent to which things are as one wishes.

All of those (admittedly vague) descriptions appear to me to be pointing to a single (admittedly vague) thing, and that is what I call happiness. Does that help?