I have found this same thing to often be true. If I know that I'm taking Thursday and Friday off, I can easily get my work done for the week in the first 3 days. However, if I try to work that hard and get "Extra" things done in an entire week, I might end up burned out. My solution is to show up to work 30-60 minutes early. In that time, I get my intense work in, accomplishing the important tasks and setting up the rest of the day to accomplish what I want to accomplish. What I end up with is a very successful morning, and in the afternoon I get to choose between going home early because I've done what I want, or sticking around to finish stuff up that isn't as important. Either way, I end up feeling great about my job!
