“You ask if I would agree to live my 70, or rather 73, years over again? To which I say Yea. I think with you that it is a good world on the whole, that it has been framed on a principle of benevolence, and more pleasure than pain dealt out to us.
There are indeed (who might say Nay) gloomy and hypochondriac minds, inhabitants of diseased bodies, disgusted with the present, and despairing of the future; always counting that the worst will happen, because it may happen. To these I say: How much pain have cost us the evils which have never happened?
My temperament is sanguine. I steer my bark with hope in the head, leaving fear astern. My hopes indeed sometimes fail; but not oftener than the forebodings of the gloomy. There are, I acknowledge, even in the happiest life, some terrible convulsions, heavy set-offs against the opposite page of the account. I have often wondered for what good end the sensations of Grief could be intended. All our other passions, within proper bounds, have a useful object… I wish the pathologists then would tell us what is the use of grief in the economy, and of what good it is the cause, proximate or remote.”
Thomas Jefferson, writing in a letter to John Adams on April 8th, 1816, which you’ll find along with other gems in The Adams-Jefferson Letters: The Complete Correspondence.