Here are a few of my fave's...
My add to the list would be Schedule time for yourself. At work when you need to get something done, you can go off and schedule a meeting with yourself. My Boss's Boss a few jobs back would do this; Take over a conference room for an hour to get something done. The rule being he was in a meeting, and could only be validly interrupted if you would interrupt a normal meeting. Result? He had time to get stuff done and we all knew to leave him alone.
A project always takes three times longer than you anticipate. So plan shopping trips, drives to the store, getting the family ready to go to the party. If you build in an extra 15 (or 30!) minutes of lead time, that heavier-than-usual traffic will not tip you over into road rage and ruin your holiday spirit. Accept less than perfection: You know when you're working on that special report and you reach the point when you say, "OK, that's it. That's all they get." The same thing applies to Christmas presents. Accept that there is no perfect one.
In your heart you know that the odds are whatever you give might be the wrong color. Or not the exact shade of the right color. One size too small. One size too big. If your objective is to be perfect, you set yourself up for failure. Aim for that golden mean, give your gift with a big smile and a hug and enjoy life.
Given my wife's family (now 36 grandkids, 17 adults, and various friends of family) there are times where you need to get away. Take a walk, hide outside, whatever. If it helps reduce your level of stress or overwhelmedness (god help me when the grammar police see that miscarriage of verbage) will help you enjoy the holidays. Trust me, your family will understand.