What do you do if your computer stops working? Do you a) try to fix it yourself, or b) call the helpdesk immediately? What would you do if the handle broke on your dishwasher? Would you a) fix it with gaffer tape or b) buy a new one? How about if you needed to strain 5 gallons of damson wine? Would you a) go to the homebrew shop in the morning and buy a ready made wine straining apparatus, or b) rig something up with a plastic sieve, a kitchen chair and a few cast iron pans utilised as counterweights? If you answered a, a, b you have what it takes to be self sufficient.
The term "self sufficiency" has all sorts of nuances that go beyond "people who grow all their own food". One meaning of "self sufficiency" is "capable, practical, skilled at day-to-day problem solving". My grandfathers both had it in spades, and both my parents had it to some extent, especially my mum. She would have a go at anything. She was especially skilled at working with textiles and ceramics, but she'd try her hand at bricklaying (and also demolition), plastering, woodwork, sculpture, plumbing, carpet laying, you name it. It's a quality that's increasingly rare. People would prefer to call a tradesman to do their painting and decorating. Mum wouldn't have dreamed of it and neither would I.
On the other hand she was a fan of things like the Betterware catalogues. I hate those. A special gizmo for cleaning down the back of the fridge? A doohicky that cracks eggs? Something to store your dishcloth on when it's not in use? I can solve those problems myself without paying someone £10 for a bit of plastic to do it for me. Because I'm self sufficient.