Answer:
Well, if you were the only person living on earth, there would be no hope for humanity. There would be no one else of the other gender to reproduce to bring more humans in the world, so what I would do was make the best of it. Grow plants, so that Earth can stay green. Enjoy every last minute you have, and do what you've wanted to do, because if you're the last person just know, you'll get to see everyone again soon.
Also, how did I become the last one alive?