Henry Wadsworth Longfellow Quote

Alas! it is not till time, with reckless hand, has torn out half the leaves from the Book of Human Life to light the fires of passion with from day to day, that man begins to see that the leaves which remain are few in number.

Hyperion, book iv. Chap. viii. - Bartlett's Familiar Quotations, 10th ed. (1919)