1. Take a whole week off.
A whole week.
No training, no guilt.
Take a whole week to yourself.
That doesn't mean you CAN'T run or om or what-have-you. But It means taking a full break for a breather. Your body will thank you, you'll feel more energized and eager to work out again, and you'll be reminded of what it's like to have one less thing on your to-do list.
2. Food log
It sucks, I know. But we need more fuel during training than during the off-season. The problem is that we stop training as much, but continue to eat the same. Time to check yourself. Check your macros, your calorie intake, your vitamin balance. Companies like My Fitness Pal are free to download, easy to use, and give you all that information with a pretty little bow on top so that you can see exactly what you're great at eating, and what you should back off on.
Spoiler: Holiday cooking will doom your macros. Have fun with that.
3. Ask a non-fitness friend out for a friend-date, your treat.
All season your less-crazy friends have been putting up with working around your training and race schedules, dealing with you being a picky eater, and listening to you ramble on about stuff they simply don't care about.
Ask a friend out, on you. Give them a break from the fitness talk to remind them that you have stuff in common still and appreciate them accepting your fitness-crazy lifestyle. Ask them about THEIR life: love, family, work, dog, holiday shopping, etc.
4. List your weaknesses.
Off season still comes with homework. It's time to start being honest with yourself.
What have you slacked on this year?
What did your races have in common on the weak end? What could you have done better during your training to feel stronger with your finishes?
Writing out that list will make it a reality, and help you when you start building a training plan for the new season.
5. Pick your A races.
Your "A" races are the races that your training plan will be centered around.
Do you have a Spartan Race Ultrabeast planned next year?
Championship of some time?
How about your first full marathon?
You shouldn't have more than 3 "A" races on the schedule, as it can start making the training plan complicated. Pick them, make sure they either build on each other or have a solid gap of time in between, and then you can start building your training plans for them. That will also help you know when your Off-season becomes On-season.
In other words, it tells you how much longer you get to be a lazy bum eating holiday cookies.