I would be sad for the first hundred years, and then I’d creep toward apathy after realizing there’s no way out. After that, I’d stop making new friends and forming new relationships. I wouldn’t want to get close to anyone. People would cease to be people in my mind; they’d just become bodies with no lasting impact.
Society would change at a pace I wouldn’t be able to keep up with, so I would distance myself from that, too. And I wouldn’t have anything worth doing, because when you have all the time in the world, you probably’ll just keep putting it off till an unreachable tomorrow. All my hobbies and my job would become meaningless, since I’d have no one to share them with, and no retirement to look forward to. And yeah, I’d still have to work. Until society collapses.
The skies would fill with smog, cities filled with hunger and plagues, the world torn apart by wars and unavoidable ruin, and I’d still be there. Alone and apathetic. And I would have to keep living, even when every other human is gone.
Sadness doesn’t encapsulate that feeling.