So, you know without any possibility of reprieve you’re gonna die or vanish.
You are positive this will happen, in say, 10 days.
You’re not on death row. You have freedom and access to your own assets.
What would you do?
Find a good home for my dogs.
Besides taking care of things I should have already done like making a will and burying some hatchets, I’d probably just experiment with some mind altering drugs at the beach between surf sessions.
Fix a TV.
Piss Tommy off? 
Go on a diet. Start exercising. Learn to play guitar.
Write emails to maybe 50 different people giving them a piece of my mind - some good, some bad.
Post lots on Facebook and social media as well.
Travel, go on a cruise, etc.
I would stock up on vodka, rum, and Caesar mix. Then I’d get drunk and stay that way until the predicted The End.
Now that I think of it, I think I just described my life! 
That’s demonstrably an upstanding mission.
Seriously, though, I need more information. Am I going to just cease existing at a given moment in time? Am I going to feel it coming? Do I get to just go to bed and never wake up again?
10 days you’ll cease to be. Die, vanish, get taken by Aliens. Whatever.
No illness or accidents.
Just gone.
I have some chocolate, do my last variety puzzle, and be thankful Imma finally see my son again.
Is this something the rest of us are supposed to understand?
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Go see my kids and grandbaby.
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Actually compile that list of people to be notified when I’m gone.
Quickly hand off some of my goods to others.
Make sure the apartment mgmt knows to check on my unit so I don’t just rot here and stink up the place.
Write what I want done with my remains, who to notify, etc. and post it in an obvious spot.
Maybe throw a party.
This has always been my dream…
I’ve always said that I wouldn’t mind dying if I can get a week or two’s notice. In my scenario the Wise Old Small Town Doctor walks into the exam room and says “I have some bad news and some awesome news: Incurable disease, you’ve only got ten days to live. But on the bright side, I brought DONUTS!”
And he whips out a dozen just for me, and another dozen for my friends and family who are treating this like a surprise party, and they’ve brought a boom box, a liquor cart, and all the fattening foods that I love.
Make it funnel cake and I’m there too.
Can I tell other people, or do they just have to think I’ve lost my marbles when I suddenly hug them and tell them how much I’ve enjoyed their presence in my life?
Yes. You can.
Get a $150 (at least) bottle of single-malt Scotch, fire up a $100 (at least) Havana cigar and wait for the end.
Yes, I have both. The former in my liquor cabinet, the latter in my humidor.