There is no substitute for persistence! It cannot be supplanted by any other quality! Remember this, and it will hearten you, in the beginning, when the going may seem difficult and slow.
Those who have cultivated the habit of persistence seem to enjoy insurance against failure. No matter how many times they are defeated, they finally arrive up toward the top of the ladder. Sometimes it appears that there is a hidden Guide whose duty is to test men through all sorts of discouraging experiences. Those who pick themselves up after defeat and keep on trying, arrive; and the world cries, “Bravo! I knew you could do it!” The hidden Guide lets no on enjoy great achievement without passing the persistence test. Those who can’t take it, simply do not make the grade.
~ Napoleon Hill, Think & Grow Rich (1937)