Adam Clarke on Ecclesiastes 11:9

Rejoice, O young man, in thy youth - Youth is devoid of cares; and, consequently, of many perplexities and distresses. Were it not so, we should have no old men; nay, perhaps not one even of middle ape. It is in the order of a most gracious God, that the young should rejoice in their youth; but they should make such a moderate use of all their enjoyments, that they may not be confounded in the day of judgment. But, O young man, if thou wilt follow the propensities of thy own heart, the noisy mirth of the fool, and the dissipation of the profligate - go on; take thy full swing; but take this with thee, that "for all these things, God will judge thee;" and if the righteous are scarcely saved, where shall the ungodly and the sinner appear?