What seems to affect me the most is the time I go to sleep. If I do get to sleep before 11 I generally feel very refreshed. Sleeping the same number (I assume, ignoring interruptions I don't remember) of hours but beginning 12, or later, end up with me feeling groggy for the morning.
The older I get, the earlier I am starting to feel tired, and the earlier I want to wake. I have friends who are very much the opposite, so we are definitely not all wired the same.