“Bad times have a scientific value. These are occasions a good learner would not miss.”

L'anisotropie de l'espace. La nécessaire révision de certains postulats des théories contemporaines. Les données de l'expérience (1997), p. 591

Source: Liberty, Equality, Fraternity (1873-1874), Ch. 2

St. 18
The Present Crisis (1844)
Context: New occasions teach new duties; Time makes ancient good uncouth;
They must upward still, and onward, who would keep abreast of Truth
Lo, before us gleam her camp-fires! we ourselves must Pilgrims be,
Launch our Mayflower, and steer boldly through the desperate winter sea,
Nor attempt the Future’s portal with the Past’s blood-rusted key.

The Value of Science (1955)
Context: Of course if we make good things, it is not only to the credit of science; it is also to the credit of the moral choice which led us to good work. Scientific knowledge is an enabling power to do either good or bad — but it does not carry instructions on how to use it. Such power has evident value — even though the power may be negated by what one does with it.I learned a way of expressing this common human problem on a trip to Honolulu. In a Buddhist temple there, the man in charge explained a little bit about the Buddhist religion for tourists, and then ended his talk by telling them he had something to say to them that they would never forget — and I have never forgotten it. It was a proverb of the Buddhist religion:To every man is given the key to the gates of heaven; the same key opens the gates of hell.What then, is the value of the key to heaven? It is true that if we lack clear instructions that enable us to determine which is the gate to heaven and which the gate to hell, the key may be a dangerous object to use.But the key obviously has value: how can we enter heaven without it?

Source: The Way of Kings

As quoted in The Pleasures of Diaries: Four Centuries of Private Writing (1989) by Ronald Blythe, p. 3
As quoted in Diaries of Ireland: An Anthology, 1590-1987 (1997) by Melosina Lenox-Conynghim, p. vii
Variant: Only good girls keep diaries. Bad girls don't have time.

Source: He's Just Not That Into You: The No-Excuses Truth to Understanding Guys

So don't worry if now your time is bad it's making you strong so nothing can effect you in future

Source: A Long Way Down