Jamieson, Fausset and Brown on Ecclesiastes 7:25

25. Literally, "I turned myself and mine heart to." A phrase peculiar to Ecclesiastes, and appropriate to the penitent turning back to commune with his heart on his past life.

wickedness of folly--He is now a step further on the path of penitence than in Ec 1:17; 2:12, where "folly" is put without "wickedness" prefixed.

reason--rather, "the right estimation" of things. Holden translates also "foolishness (that is, sinful folly, answering to 'wickedness' in the parallel) of madness" (that is, of man's mad pursuits).