Don't be afraid of the freezer
Take pasta sauce, for example. Unless you are feeding a family with quite a gnocchi problem, you generally only need about a quarter to a third of the red sauce in the jar -- the rest might end up sitting on a shelf, waiting for its inevitable trip to the bottom of a Glad bag. Stick that sucker in the freezer, and wait for the next time ravioli calls to you.
And this extends to full meals, as well.
I generally don't like to eat the same thing two days in a row, but I am constantly finding myself with leftovers. I bought some cheap-ass Tupperware, started freezing my excess meals, and found them just fine to eat days later.
And buying pre-frozen foods, obviously, will increase their shelf life. According to Gunders' book, frozen food can be, and often is, just as nutritious as fresh food. Even cuisine that might appear a little dubious in your freezer should actually hold out.
Harvard professor and chef Barton Seaver tells Gunders in the Waste-Free Kitchen Handbook that, "The technology of freezing fish has evolved to the point where it's comparable, if not better than, fresh fish."