Charles H. Spurgeon on Psalms 141:4

Incline not my heart to any evil thing, etc. The present pleasure and commodity of sin is in high estimation with the sinner, and much sweeter to him than what he may lawfully enjoy; the pleasures of sin are his delicates. No man can keep himself from being taken with the allurements of a sinful course, except the Lord preserve him: Let me not eat of their dainties. The holiest men in Scripture have been most sensible of the impotency of their own free will, and of their inability to resist temptations, or to bring the principles of grace into action; most diffident of themselves, most dependent upon God, most careful to make use of means, and conscientious in following of ordinances, as their prayers do testify: "Incline not my heart to any evil thing", etc. —David Dickson.