The heart is where one believes so we have to take care of our hearts. Jesus Himself told us to guard our hearts.
The heart is the place of knowing God loves us, the place of knowing we can rest and trust God, the place of knowing Someone knows all our hopes, sins, and quirks, and yet loves us.
It really is about meditating. The Bible tells us to meditate on the word. Nowhere in the Bible does it tell us to study the Word of God. Some folks will say that the Bible tells us to "study to show ourselves approved." But only the KJV has that translation and the real meaning is "be diligent to." The Bible however tells us everywhere to meditate on the word. So the Word of God is not a thing to be studied and argued about. It's not a thing to be understood or mentally taken apart. To be effective, the Word of God must not live in our mind but in our hearts. The word is sowed in our hearts, not our minds. Break up your fallow ground means break up your hearts. Lift up your heart to God means just that: lift up your heart.
We are to ponder the words in our hearts. Mary pondered the words in her heart. We are not to ponder them in our minds. We are to let the Word of God stay in the imagination of our hearts. Mentally, we don't know what it is to dwell in the secret place of the most high. We cannot by our minds understand "The Lord is our Shepherd." But we can ponder and meditate on the images God has given us. That is when the word grows. That is when our prayers are answered. That is when the word of God transforms us. The word doesn't transform our mind. The mind is only changed when the heart has been transformed. Reason is in the heart. Even anatomy tells us that. When someone gets damaged in the part of the brain that deals with emotions, their "reasoning" ability goes. So scientists are saying that reason is created from emotion.
If we love God in our hearts, our minds will follow. If we meditate on God's words in our heart and ponder His promises in our hearts, the promises will manifest because the seeds planted in those promises will have found good ground.