Shachimin

“A certain man who was learning archery faced the target with two arrows in his hand. But his instructor said, ' A beginner ought never to have a second arrow; for as long as he relies upon the other, he will be careless with his first one. At each shot he ought to think that he is bound to settle it with this particular shaft at any cost.' Doubtless he would not intentionally act foolishly before his instructor with one arrow, when he has but a couple. But, though he may not himself realize that he is being careless, his teacher knows it.
You should bear this advice in mind on every occasion. (In the same way) he who follows the path of learning thinks confidently in the evening that the morning is coming, and in the morning that the evening is coming, and that he will then have plenty of time to study more carefully ; less likely still is he to recognize the waste of a single moment. How hard indeed is it to do a thing at once-now, the instant that you think of it !”
― Yoshida Kenko, Essays in Idleness: The Tsurezuregusa of Kenkō