At these time of the year, swimming, cycling or swimming isn't the main objectives that all athletes or triathletes have.
We think about gifts we should offer to our family. But the sport isn't out for us, it is more a pleasure than a training when we go outside for cycling, running or to the swimming pool for swimming sessions.
As our meals are, most of time consistent, we can make some longer training as if we were in a ditetical period, so we don't have to listen to our training plan to reduce some effort or go home after a delimited time of sport.
So in December, do what you want in sport because you can eat what your stomach can't the rest of the year!