I feel your pain! I seriously suffer from Seasonal Affective Disorder, so these short days are so dreary. I combat the blues in a few different ways:
1) Go outside any time the sun is out, even if just for a half hour or so; 2) Install "broad spectrum" light bulbs, which give a natural light feel to even the darkest of rooms and perk up your mood; 3) If you have a fireplace, enjoy it now! 4) I keep track of the sunrises and sunsets in my daily newspaper. Each day the sun rises a minute or so earlier, and sets a minute or so later. Somehow, psychologically, this keeps me going, knowing that every day after December 21st is just a tad bit longer.
Can you plant something indoors? Force some spring bulbs? The sight of anything growing gives hope for the future.
"When life itself seems lunatic, who knows where madness lies?"