I know finishing a knitting project is not going to "save the world" but hopefully you'll be inspired to pick up something that you haven't quite got around to finishing yet.
Here's some quotes on Persistence:
B.G. Jett: "If the word quit is part of your vocabulary, then the word finish is likely not."
James Whitcomb Riley: " the most essential factor is persistence - the determination never to allow your energy or enthusiasm to be dampened by the discouragement that must inevitably come."