Because this is the shortest day of the year, this is a day when many people are at their lowest as far as mood is concerned. Me too.
But then I think that if John Donne was affected by the calendar, I can overcome it and do something productive. You too.
And from here on, it can only get better. That’s what Donne says:
Since she enjoys her long night’s festival,
Let me prepare towards her, and let me call
This hour her vigil, and her eve, since this
Both the year’s, and the day’s deep midnight is.