I'm best late at night. I'm a freakin' wreck in the morning, unless the rather excellent gal I'm dating happens to be in bed with me (instantly no anxiety!). There must always be several hours between when I wake up and when I have to do something particularly stressful.
For me this also has to do with having low blood sugar (and low blood pressure). Until I've consumed a huge quantity of sugary beverage (usually OJ) and eaten something, I'm slightly-disoriented and generally unable to think straight.
I do always feel better after a meal, regardless of the time of day.