Morning is the best time to exercise for me.
I run in the morning and feel great the whole day. I think I can say that I am “energized” for the day. It's a good time to think clearly, plan my day, and relax mentally.
Starting the morning with running, before other distractions can intrude, is my best fitness habit. It assures that something else won't crowd exercise out of my schedule. When my days get hectic, exercise is likely to take a back seat.
And for those who are less motivated, if you exercise in the morning, it helps you to stick with it.