Matthew Poole and continuators on Ecclesiastes 1:18

18 For in much wisdom is much grief : and he that encreaseth knowledge increaseth sorrow .

Or, indignation, or displeasure within himself, and against his present condition.

Which he doth many ways, partly because he gets his knowledg with hard and wearisom labour, both of Mind and Body, with the consumption of his Spirits, and shortning and imbitterment of his Life; partly because he is oft deceived with knowledg falsly so called, and oft mistakes Errours for Truths, and is perplexed with manifold doubts, from which ignorant Men are wholly free; partly because he foresees, and consequently feels the terrour of many miseries which are, or are likely to come to pass, which are unobserved by less knowing persons, and which possibly never happen; partly because he hath the clearer prospect into, and quicker sense of his own Ignorance, and Infirmities, and Disorders, and withal how vain and ineffectual all his knowledg is for the prevention or removal of them: and partly because his Knowledg is very imperfect and unsatisfying, yet increasing his thirst after more Knowledg, and consequently after more dissatisfaction, because instead of that just Honour, and Delight, and Advantage which he expects from it, he meets with nothing but Envy, and Opposition, and contempt, because his Knowledg quickly fades and dies with him, and then leaves him in no better, and possibly in a much worse condition than the meanest, and most unlearned man in the World.

Marginal references: Or, indignation.