The Lord is my strength and my shield; My heart trusted in Him, and I am helped; Therefore my heart greatly rejoices, And with my song I will praise Him.

Psalms 28:7

King David was a good shepherd, mighty warrior and king; but he came to understand that his strength came from the Lord.   His strength did not come from his skill, his victories or his earthly authority; but his strength came from the Lord with whom he trusted. 

David discovered his strength came when he clung to God and as a result his heart was a peace.  David could rejoice and sing in the midst of his circumstances because of his grip on God and God’s grip on him.

⁷ Because you are my helper, I sing for joy in the shadow of your wings.
⁸ I cling to you; your strong right hand holds me securely.

Psalms 63:7-8

David discovered that when you place your trust in the One who is eternally trustworthy and forever strong you will not only receive an outer strength to endure, but an inner strength that gives a peace.  And that peace gives an assurance in one’s heart, that they are not alone and without help.

As you go about your day, forge ahead with full assurance in your heart; do not be afraid or discouraged; because God, in whom you trust, has got a hold on you and will strengthen you and hold you up with His victorious loving hand.

Don’t be afraid, for I am with you. Don’t be discouraged, for I am your God. I will strengthen you and help you. I will hold you up with my victorious right hand.

Isaiah 41:10