How does one arbitrate the conflict between present happiness and future happiness?

It's a question I've journaled about on many an occasion without yet reaching any conclusions. Basically, if you focus too much on present happiness, then you'll neglect to do the necessary work to provide for your happiness in the future. On the other hand, if you focus to much on future happiness (by working or studying all the time), then you'll never get to experience that happiness, because you're always working towards a future that never arrives.

I think I'll take to calling this "the question of life," because it seems to be at the heart of a lot of other difficult life questions. For instance, sometimes I have trouble deciding what to do with my time. Exercise, homework, sleep, what? Often it comes down to a conflict between what I "should" do and what I "feel like" doing, which is exactly the conflict between future happiness and present happiness.

I'm really interested to hear anyone's opinions about this question, especially if it's something you've struggled with in the past. It's the "biggest" question I know, but I figure lucid dreamers are probably fairly thoughtful folk.