“A violent wind does not outlast the morning; a squall of rain does not outlast the day. Such is the course of Nature. And if Nature herself cannot sustain her efforts long, how much less can man!”

"To an Old Lady" (1928), line 1; cited from John Haffenden (ed.) The Complete Poems (London: Allen Lane, 2000) p. 24.
The Complete Poems

Up-Hill http://unix.cc.wmich.edu/~cooneys/poems/rossetti.uphill.html, st. 1 (1861).

Ce que la nature fait avec beaucoup de temps, nous le faisons tous les jours, en changeant nous-mêmes subitement, par rapport à un végétal vivant, les circonstances dans lesquelles lui et tous les individus de son espèce se rencontroient.
Philosophie Zoologique, Vol. I (1809), p. 226; translation by Hugh Elliot, Zoological Philosophy: An Exposition with Regard to the Natural History of Animals (1914), p. 109.

Source: A Vindication of the Rights of Woman (1792), Ch. 3
Context: Should it be proved that woman is naturally weaker than man, from whence does it follow that it is natural for her to labour to become still weaker than nature intended her to be? Arguments of this cast are an insult to common sense, and savour of passion. The divine right of husbands, like the divine right of kings, may, it is to be hoped, in this enlightened age, be contested without danger, and though conviction may not silence many boisterous disputants, yet, when any prevailing prejudice is attacked, the wise will consider, and leave the narrow-minded to rail with thoughtless vehemence at innovation.

Source: Morals and Dogma of the Ancient and Accepted Scottish Rite of Freemasonry (1871), Ch. XIX : Grand Pontiff, p. 312
Context: The true Mason labors for the benefit of those that are to come after him, and for the advancement and improvement of his race. That is a poor ambition which contents itself within the limits of a single life. All men who deserve to live, desire to survive their funerals, and to live afterward in the good that they have done mankind, rather than in the fading characters written in men's memories. Most men desire to leave some work behind them that may outlast their own day and brief generation. That is an instinctive impulse, given by God, and often found in the rudest human heart; the surest proof of the soul's immortality, and of the fundamental difference between man and the wisest brutes. To plant the trees that, after we are dead, shall shelter our children, is as natural as to love the shade of those our fathers planted.

Variant: A man can be happy with any woman, as long as he does not love her.
Source: The Picture of Dorian Gray