Being truely self-sufficient is for the hard-working few, and even then they will still need to purchase or barter for things made/produced by others, but to a lesser degree than the rest of us.
My grandparents lived in Northern Ontario, Canada, out in the bush country, and they were nearly self-sufficient, but it was a very hard life that drove their 3 children to leave home as soon as they were about 15 and could earn a living for themselves to escape what was a very hard life and my Grandfather a very hard task master. When the human source for free labor left, my grandparents sold their farm and moved to the city. Today it's more of an old-fashioned romatic notion to be self-sufficient.
But that doesn't excuse us from doing what we can with what we have. I also think nearly everyone can be a little more self-sufficient by incorporating a few simple things in their lives like growing some of the food they consume and learning where they can get free food from neglected fruit trees, berry bushes, plum thickets, nut-producing trees, and keeping a well-stocked home to help during times of emergencies.
My biggest challenge would be meat. Even if I produced it by having a few chickens or a hutch of rabbits (which are legal to have in certain numbers in the city limits), neither hubby nor I could kill and dress an animal. That's where I would have to draw the line. Although I helped with that sort of thing when I was a kid and we dressed chickens, I was the feather-picker, and wouldn't have anything to do with the icky stuff. I'd have to barter with a neighbor who needed bread, or something else I could readily produce that they couldn't, to do our "dirty work" for us on any animals.
For an interesting side note associated with being self-sufficient, here's a web site on raising fish in a barrel.
http://www.tabletophomestead.org/Raising%20Fish%20In%20A%20Barrel.html
This past week during an ice storm was a good example of people suffering from indifference to taking care of themselves and how they think it's someone elses job. Even with full knowledge of a pending storm they didn't bother to stock food and had nothing with which to provide some kind of warmth. Several friends of ours who live in big fancy homes out in the middle of nowhere are seeing the need to be a little more self-sufficient in the future. They failed to have even simple things like batteries for flashlights, water they could use for drinking and washing, a way to prepare and keep food when you are several days without power. People were calling the local radio station and complaining that FEMA should be providing gas-powered generators to everyone who were without power due to storm damage (and one week later, there are still people without power). I'd better quit before I get on one of my soap boxes and preach about the difference between being stupid and being ignorant.
~Gingerbread