Psalms 19:14 let the words of my mouth and the meditation of my heart be acceptable in your sight o lord my rock and my redeemer
Meditation is a word we use for focusing on something. The desires of our hearts are the things that we could consider while meditating. We are always reflecting on something, focusing on something and thinking about something. There is never a moment that we aren't considering something with our senses. So when the bible says to meditate on God's law, or God's word, it is basically just telling us to think about it, focus on it,read it, take it in and digest it. Let it be continually on our minds. This will help us to show Him our love for Him because it will help us to be obedient to Him. Jesus said if you love me keep my commands. Christian should know how to reflect on the bible, not just certain portions that make us feel good but the entire bible is important so that we better understand God's heart and God's desires. David says; let all the meditation of my heart be pleasing to you Lord. Everything that we are focusing on throughout the day should be pleasing to God. God tells us what to focus on in the book of Philippians 4 verse 8.