When the word "persistence" arises, I must admit that this AA (Alcoholics Anonymous) saying is one of the first things that comes to mind. I'm not AA myself, but know some about the organization, and I'm willing to bet that most folks have heard of and/or followed a "one day at a time" philosophy at one point or another.
It's a great philosophy for encouraging persistence. You don't have to complete that "to do" list in one marathon session, you don't have to climb that entire mountain in one enormous leap, you don't have to sit down and write your way from beginning to end of a writing project in one fell swoop... You simply take your list one item at a time, climb that mountain one step at a time, write that project one word at a time.
You don't live life all at once: all of its joys and sorrows, the triumphs and defeats. It's moment by moment, day by day.
And now, here's a low-key YouTube video (with some relaxing music) about the power of persistence. Enjoy!