The trick to working better and improving work productivity is not to work harder and burn the midnight oil as some would think. It's to take a break and also to do less!
This has been something I have been trying to tell all the people who work with me. It's important to do LESS and do it better than to take on too many things on hand and then deliver poorly. And now, Harvard Business Review has a research report out that confirms this view. You can find the link to a detailed report here on the Wall Street Journal
So, focus on quality of delivery. Do less. Learn to say NO to tasks building up to overwhelm you.