This is a proof of a well-trained mind, to rejoice in what is good and to grieve at the opposite.
"Hoyt's New Cyclopedia Of Practical Quotations" by Jehiel Keeler Hoyt, De Amicitia, XIII, p. 326-29, 1922.

This is a proof of a well-trained mind, to rejoice in what is good and to grieve at the opposite.