As glass, remarked, it's almost tempting Fate to say 'Yes, I'm happy', but we can't go through our lives being worried about feeling happy in case something happens to take it away from us. Like others were saying, if my family are happy, then I am. I think I've got to the point where I do try to weigh up situations before diving in and trying to sort everyone's happiness for them.
If I feel low, I find that going for a long walk sorts me out somewhat, and the same can be said for music. I don't have earphones in when I'm out in the countryside, because I like to hear the sounds of Nature, but if I'm on a bus, I do wear them and listen to my favourite stuff.
If I get very sad about something, I try to count the blessings that I do have. And I do have so many.