Have you ever thought about the time of day when you are most alert and productive? This would be your "Window of Peak Performance." For many people it is early in the morning, a couple of hours after waking. For others, it is late at night when it is quiet and the rest of the world has gone to sleep.
Whatever your "window" is, it is important to align your most challenging work with that window. And when you are feeling sluggish (often around 3 or 4 PM when we go for coffee or a sugary snack) try to use that time for more routine tasks, such as checking email or submitting expense reports.
Being mindful of our Windows of Peak Performance improves both our efficiency and productivity.