I only work on projects I have a deep interest or passion for. Nothing kills motivation more than non-interesting work. A close second is ensuring you're on a

I only work on projects I have a deep interest or passion for. Nothing kills motivation more than non-interesting work. A close second is ensuring you're on a great team. I agree w/other comments that taking breaks helps, but I haven't found that to be as important as those two (passion and team). You can take as many breaks as you want throughout the day, but if you're stuck having to return to non-interesting work or a team you'd rather not work with, you'll still find it hard to get motivated and maintain focus.