I would not be self-sufficient until I made my own chips, with which to build a computer to get on the Web to make this post.
It's impossible to be self-sufficient while living surrounded by today's technology. Ted Kaczynski, the Unabomber, lived as a survivalist in a shed in the mountain, but he still came into town occasionally to get "stuff".
Robinson Crusoe, a fictional character in a 1719 novel, lived for 28 years on an isolated island after being shipwrecked. He was about as self-sufficient as it could be, after he got bootstrapped with some tools he salvaged from the wrecked ship.
No, I doubt that anyone could be that tough. And if he were, he would not have the means to frequent this forum or surf the Web.