Psalm 141 is an evening prayer (v.2). David calls up on the Lord to protect his words and his heart from every evil thing. There were wicked men all around who would entice David to join him in their ‘dainties’ (sensual pleasures). They would try to ensnare him and entrap him (v.9-10). So David looked to the Lord for help and protection (v.8). He opened himself up to the rebukes of the righteous, which would be like a blessing, like oil on his head (v.5).
We live in a world of many temptations and snares. Many people would want to turn us away from the Lord. We need God to protect us, to help us guard our hearts, our words, and our actions. We need the strength that only He can give so that we don’t fall into these sinful temptation.