A hero does not stand still or set himself limits. A Guynemer looks on one victory as a rehearsal for another; with unfailing vigor he makes flight after flight, closes with an adversary, turns round on another, and only in death sees the end of his career.
We must always seek, always endeavor. Nature makes the wilderness flower anew, the star to shine, the water to flow down slopes, round obstacles, into empty places, dreaming of the sea that waits it yonder, and which it may at last reach. Creation in every one of its stages is continuous aspiration. The mind which is potentially all things can of itself no more limit its ideal forms than the natural forms of which they are a reflection.
Death will set the limit, and so will our own inadequacy: let us at least have the courage to flee the frontiers marked out by laziness. Infinity, lying for us, demands infinity in our desire, to correct as far as may be the gradual failure of our powers.
– A.G. Sertillanges, from The Intellectual Life: Its Spirit, Conditions, Methods, 126-7.