Imagine suddenly you no longer exist, poof, from one day to the next there is no more you.
What if you knew that this day would come in a month?
What if it wasn’t for another year?
Or in 5 years?
Would you spend your remaining time differently than you do now?
If so, why aren’t you already doing it?
On the last day I’d throw a big party. Then as my time approached I’d say: “Attention everyone! There’s something I never told you. My real name is Sergius of Proxima Centauri! I come from another planet! And it is now time for me to beam up to my spaceship. Somebody film this please…” Then I’d sit in a full-lotus position til I disappeared.
No, seriously, I’d just double-check my will and give away most my personal stuff, then go on living like always.