Rule n. 1 - If you have time to log on facebook, you also have time to train
Rule n. 2 - There's a minimum number of kilometers you have to run each week. However, you can run more than the minimum goal.
Rule n. 3 - If you really can't stand running one more kilometer, you are not allowed to give up. You are allowed to hop down the treadmill and on the elliptical instead, as long as you'll do 12 minutes on the elliptical for every km skipped.