Pick one easy thing you can do for your fitness and health.
Don't pick something hard you can't be sure to sustain. So no "stop drinking beer forever" or "no more snacks" or "I'll do 10 minutes of interval cardio."
Pick something easy, like, "No soda at lunch today" or "Go for a walk" or "Sit and work on breathing from my diaphragm for 5 minutes" or "Couch Stretch for 1 minute each side." Something you can and will be able to do today.
Do that thing today.
Not tomorrow, not from Monday, not after the holidays.
There is no tomorrow, there is only today.
Pick that thing, do it today, and just get it done. It's not a complete day until you finish it.
There is no tomorrow, there is only today. Do it today.
So go for a walk. Do 20 air squats before lunch. Get in that stretch for your bad hip. Easy and doable.
Tomorrow? Tomorrow get up and try that again. The same thing, if possible. Make a habit of it. Don't add anything else until you've got this one under control. Get an easy positive step today and get going.
Don't pick something hard because it's the "best" thing you can do. You don't want to let the enemy be the perfect of the good. Don't overanalyze. Just simple and easy. A walk. A few veggies with lunch. Some water instead of juice. Easy.
Already in shape, hitting the weights, diet is on point? Good, keep it up. And find something easy that you're letting slide (that stretch you hate, that warmup you said you'd do every day, that tendency to stick a candy bar into your lunch bag on Fridays) - and do that.
Just get it done.
One easy thing.
And do it TODAY.