“The LORD is my strength and my shield; my heart trusted in him, and I am helped: therefore my heart greatly rejoiceth; and with my song will I praise him” (Psalm 28:7). David had moved from The Lord is “our” strength to the Lord is “my” strength. Jehovah would supply the strength he needed for that moment. The key is in these words, “my heart trusted in him.”
Lauren Daigle has a beautiful song called “You Say.” She noticed the key as well. One line is about God saying she is strong but she feels weak. Her response was “I believe.” The key to transferring what you need such as strength is believing what God says. We believe what God says. We read (what God says) in the Word, “The LORD is my strength” and we really believe that is true. As David said, he trusted in his heart. Trust is to have confidence, security, hope, and trust. It begins in the heart.