David was a teenage shepherd boy whose physical appearance showed no special feature. There was nothing physically striking about him that pointed to him as God's choice of a king-elect.
But God sees far beyound what man can comprehend.

(1 samuel 16:7).
''But the Lord said unto Samuel, Look not on his countenance, or on the height of his stature; because I have refused him: for the Lord seeth not as men seeth; for men looketh on the outward appearance, but the Lord looketh on the heart''

Though his actions weren't always perfect toward God.

(Acts 13:22) '' And when had removed him, he raised up unto them David to be their King; to whom also he gave testimony, and said, I have found David the son of Jesse, a man after my own heart, which shall fulfill all my will''

He served God with a loyal heart.

To be loyal means to be faithful or steadfast in allegiance. It means to be devoted to God's cause. This was the virtue Saul lacked that made God rejected him as king over Isreal. Another king, Amaziah, did all the right things but still didn't get God's approval because of his wrong attitude.
'' And he did that which was right in the sight of the Lord, but not with a perfect heart'' (2 chronicles 25:2)
So your relationship with the Lord, the state of your heart counts! Your attitude to God and to service in His Kingdom must reflect wholehearted devotion and unfeigned loyalty.

May God give all of us this kind of Heart.

A Heart that fears him and is utterly devoted to his cause, which is the salvation of ALL mankind if it were possible.

It's time to examine yourself and ensure your words match your action, and that your actions match the thoughts of your heart in your service to the Lord.
Who are you, and how do you do your work for the Lord? These are very important questions you must answer for yourself.

Only the works we do with a sincere and Loyal heart will be accepted when we stand before the judgment seat of Christ; the rest will be burnt because they have no significance befor God

(1 corithians 3:13) " Every man's work shall be made manifest: for the day shall declare it because it shall be revealed by fire; and the fire shall try every man,s work of what sort it is.