In the sense that you are bringing up productive time, or when you are at your best, I vote for the morning because of something that is probably personal to me

In the sense that you are bringing up productive time, or when you are at your best, I vote for the morning because of something that is probably personal to me. I see the mornings as a time of hope and possibility ('imagine all that you can get done today'). No one says to themselves, 'oh, I hope today is crappy'. Not a surprise then that I actually get more 'depressed' as the day goes on (ie, afternoon and onward) and it's not necessarily dependent on how much I've accomplished or not, but rather that the realm of what is possible has dwindled. Coffee is also my friend. I have between 1 and 1.5 cups per day but just getting up and feeling like Success Kid, per a mix of caffeine and hope, gets me going in the right direction.