For years I noticed a burst of productivity around the holidays. stuff that had been hanging over my head for months would suddenly get done. New ideas would suddenly pop into my head.
I attributed it to things like the psychology of the calendar, or just having fewer emails to answer, or more unstructured time... But the recipe is simple:
Eat well. Sleep well. Stay connected to loved ones. Get some exercise.
That's it. That's all it really takes to complete projects, tackle nebulous fears, and poke the box.