From this psalm our hearts should be duly affected with hatred of sin, and seek satisfaction in God's loving-kindness. Here is the root of bitterness, from which all the wickedness of wicked men comes.
It takes rise from contempt of God, and the want of due regard to him. Also from the deceit they put upon their own souls. Let us daily beg of God to preserve us from self-flattery. Sin is very hurtful to the sinner himself, and therefore ought to be hateful; but it is not so.
It is no marvel, if those that deceive themselves, seek to deceive all mankind; to whom will they be true, who are false to their own souls? It is bad to do mischief, but worse to devise it, to do it with plot and management.
If we willingly banish holy meditations in our solitary hours, Satan will soon occupy our minds with sinful imaginations. Hardened sinners stand to what they have done, as though they could justify it before God himself.