((((((thunderbear))))))
Are you taking anything to help you sleep at night? I take sleeping pills for insomnia and even though I get a full night's sleep they tend to leave me feeling pretty groggy for the rest of the day. Certain cold medicines can do that to you too, if you're on that. You could also check with your doctor if you haven't already to see if maybe the tiredness is a side effect of any other medications you're taking for your depression.
Other than that, when I'm feeling particularly drained what helps for me is to keep cool. Being too warm tends to make me really sleepy. I keep my heat on low, and if it's not too cold outside I open my window to let in some fresh air. Just getting some fresh oxygen to the brain can really help.