Philippians 4:8 Finally, brothers, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable - if anything is excellent or praiseworthy - think about such things.
“Prayer for peace in my heart” is partially based on Ephesians 2:13-18 which speaks about how Jesus is our only true peace. He makes peace between you and God by ending all conflict and hostility. But beyond just an end to disagreement, true peace is a unified heart. Pray for peace in your heart and God will give it to you.