I would spend most of my time writing. Sure, I may not be able to show anyone, but without any obligations left, I would want to just write. About love, adventure, anything I could think of.
If I knew for sure that I was the last human, and there was no chance of meeting intelligent life. I would off myself. What’s the point of living if you’re doing it alone?
Honestly, I would spend most of my time being sad and regretful that I failed to keep anyone else alive. As frustrating as dealing with people can be sometimes, I would miss them.
First of all check what the hell is in Area 52!