Quote from Lucius Annaeus Seneca,
"Toward good men God has the mind of a father, he cherishes for them a manly love, and he says, "Let them be harassed by toil, by suffering, by losses, in order that they may gather true strength." Bodies grown fat through sloth are weak, and not only labour, but even movement and their very weight cause them to break down. Unimpaired prosperity cannot withstand a single blow; but he who has struggled constantly with his ills becomes hardened through suffering; and yields to no misfortune; nay, even if he falls, he still fights upon his knees."
Lucius Annaeus Seneca (more quotes by Lucius Annaeus Seneca or books by/about Lucius Annaeus Seneca)
(4 B.C.-A.D. 65) Roman Stoic philosopher, statesman, dramatist, "Seneca the Younger"
Moral Essays, De Providentia (On Providence), 2.6; translation by John W. Basore
Goodness, God, Adversity, Strength, Labor, Prosperity