John Gill's Exposition of the Whole Bible
Proverbs 15:15
All the days of the afflicted [are] evil,.... And some are afflicted all their days, from their youth up; so that not only the days of old age are evil days, in which they have no pleasure, but even the days of their youth; all their days, as Jacob says, "few and evil have the days of the years of my life been", Genesis 47:9; because they had been filled up with affliction and trouble of one sort or another. Or, "all the days of the poor" f; either in purse, who want many of the good things of life; or in knowledge, as Gersom and Aben Ezra observe;
but he that is of a merry heart [hath] a continual feast; a heart that has "the kingdom of God" in it, which lies "not [in] meat and drink, but [in] righteousness, peace, and joy in the Holy Ghost", Romans 14:17: which has the love of God shed abroad in it by the Spirit, where Christ dwells by faith; and that lives by faith on him, and on the provisions of his grace; all this is a constant continual feast to a gracious soul, made joyful hereby.
f עני "pauperis", V. L. Pagninus, Junius Tremellius, Piscator, Mercerus, Michaelis.