The first Psalm compares Jesus and His followers, those who walk in purity of heart, with those who walk in sinful paths. Christians produce the good fruits of the spirit as they drink on the pure doctrines of truth. Whereas sinful man perishes. It's important to remember that friends impact our hearts and lives. “Do not be deceived. Evil company corrupts good conduct.” 1 Corinthians 15:33

Psalm 19:14 reads, “Let the words of my mouth and the meditation of my heart be acceptable in Your sight, O LORD, my rock and my Redeemer.” This prayer is appropriate for all God’s people. Controlling the tongue is truly a difficult task. Jesus explained, “A good man brings good things out of the good stored up in his heart, and an evil man brings evil things out of the evil stored up in his heart. For the mouth speaks what the heart is full of.” Luke 6:45 (NIV). Therefore to control our words, we need to develop our hearts,” Luke 6:45 (NIV). 

The Christian’s habit of thought, where his mind returns during moments of mental leisure, is to be carefully cultivated. When the mind is not occupied by natural responsibilities, it should quickly return to thinking about the Lord. Psalm 116:7, “Return to your rest, O my soul, for the LORD has dealt bountifully with you.” (See also Philippians 4:8.) We do not want to focus our lives on laying “up for yourselves treasures on earth… but lay up for yourselves treasures in heaven….” Matthew 6:19, 20. Our thoughts prompt actions, and actions build Christ-like characters, which are obedient to God’s will, eager to serve Him.

Additionally, to further control our hearts (affections) and minds, Paul teaches us to “Pray without ceasing,” and “Study to shew thyself approved unto God…rightly dividing the word of truth,” 1 Thessalonians 5:17, 2 Timothy 2:15. Studying and meditation work together. "Oh, how I love your law! I meditate on it all day long." Psalm 119:97.

As we do these things, we will become more and more “acceptable in His sight,” ready to be “planted by the rivers of water.”