I've spent years of my life absolutely alone; gone months without talking to another person. There isn't anything you'll do that will give you the emotional fulfillment of interacting with someone else.

As for living with yourself:

Find some sort of exercise you don't mind doing and make it non-optional. The goal isn't to go all out, just get your heart rate up for half an hour. You won't want to do it sometimes but you still have to go. You can do a crappy job at it and slack off for a day or two but you have to go out. For me this is riding a bike.

Otherwise it's good to be absorbed in something. It's not the same feeling but there is intrinsic satisfaction in learning / building / experiencing things.