The sense of exhaustion is largely from overwhelm, from fragmented attention, and a lack of insight into how to manage the brain's resources. Our bodies and brains work in cycles of expenditure and replenishment - daily cycles, weekly cycles, monthly cycles, and even the seasons dictate an ebb and flow of energy and ennui. By managing the smaller cycles effectively - enough sleep, enough fun, enough nourishment, and enough love, the bigger cycles, like the annual one have less impact and become less taxing.
So go sleep, play, eat, and love, and call me in January to discuss the neuroscience and system structures for keeping energy and enthusiasm available throughout the entire year.