Delight yourself in the LORD, and He will give you the desires of your heart (Psalm 37:4). The truth is we get to choose what we love. We can love this world and the things in it (1Jn 2:15-17); these things all pass away, they are temporary. We can choose to love the things of the Lord, His word, His mercy, His grace, His Spirit, His love, and His Son; these are eternal. We will in the end have chosen life or death. The end of the world and all the things in it is destruction. The end of those who have chosen to love this world and the sin in it will be eternal punishment, and those who have chosen to love Christ and be found in Him will find life (Matt 25:46; Rom 6:23). The Devil is shrewdly deceptive and sin is powerful (Eph 6:10-12). However, we have armor against both of these, even, a full armor in Christ Jesus (Eph 6:13-18).
David, the king, taught his son the protocol for accomplishing God’s fruitful purpose in our lives:
My son, pay attention to what I say;
listen closely to my words.
21 Do not let them out of your sight,
keep them within your heart;
22 for they are life to those who find them
and health to a man’s whole body.
23 Above all else, guard your heart,
for it is the wellspring of life (Prov 4:20-23 NIV).
Jesus, Himself, taught about the importance of the heart in bearing fruit for God, when He spoke about good trees with good fruit and bad trees with bad fruit: The good man brings good things out of the good stored up in his heart, and the evil man brings evil things out of the evil stored up in his heart. For out of the overflow of his heart his mouth speaks (Luke 6:45). Our fruit comes from the heart. This is why it is so important for us to study, pray, and worship, because it helps to guard our hearts in Christ Jesus (Php 4:4-7).