I've noticed that what I eat definitely affects my mood, if only to make me bogged down and slow. Maybe it's as you say Pen, aging, but I wonder if it's not my body telling me it's reaching it's limit with some of the chemicals we stuff our food with these days.

As far as sleep, remember the movie "They Líve." It was propaganda to make people believe in the "8 hours of work, 8 hours of play, 8 hours of sleep" bit. ^_^

Hard pressed on my right. My center is yielding. Impossible to maneuver. Situation excellent. I am attacking.
--Ferdinand Foch-- at the Battle of the Marne