People have been trying to define happiness for centuries. I tend to think of it more as an overall condition rather than a moment of happy. I'd say I'm content with things in general these days and gently amused to the point of laughter several times a week, usually by something read in a book. Overwhelming hilarity and I are pretty much strangers.
As for healthy, it's a relative thing. At 66 I have more afflictions than I did at 16. On the other hand when I was 16 people who were 66 were pretty much always worn out, decrepit, wizened, bent over, inactive, lethargic, mentally kaput and smelled funny. I am those things only occasionally, and made it up both Arthur's Seat and Tintagel last week without any real difficulty, just a slower pace than many.
