Being forced to see everyone on Earth die and then living in a world with no other humans.
I'd kill myself if there were no test-tube babies to raise or any aliens to save me.
Another big one is being completely ignored by everyone; everything I do, people would not even know I existed. If I shot someone in the face, everyone would ignore me and the action I did.
I would kill myself.
My last main fear would be waking up 100 years later.
I would be horrified, but I would definitely still be sane enough to want to live. You know when you slept through something and it was really important?
That feeling I fear.
