Searching requires looking in every place available to see what is there. Asking God to search your heart means that you are inviting him to know everything that is in it. Vulnerability is hard, particularly when we are battling pride or when we want to hide painful feelings or even sin.
Of course, God already knows your heart, so there is no point in hiding from him. But when you invite him in, you are acknowledging that you might need him to show you things in your heart and mind that need his love and guidance. Know that as you surrender to him, his love will cover all wrong, and he will lead you in the everlasting way.
Psalm 139:23-24 (NASB) Search me, O God, and know my heart; Try me and know my anxious thoughts; And see if there be any hurtful way in me, And lead me in the everlasting way.
Prayer: Search me, O God, and know my heart. Help me to put aside my anxious thoughts and hurtful ways. I want to be led in your everlasting way.