According to Cliff Arnall of Cardiff University in Wales, today is the most depressing day of the year.
His formula reads: 1/8W+(D-d) 3/8xTQ divided by MxNA, where W is the weather, D is your debt (and small d is the amount of money you'll get on your next payday), T is elapsed time since Christmas, and Q the length of time since you abandoned a New Year's resolution or other self-improvement plan. M is a sort of all-purpose category for motivation levels. NA is the necessary action for making your life better.
On the bright side, tomorrow will be a better day.