Last Sunday I spoke from 1 Samuel 16 on the anointing of David. The key verse, and a very familiar one, is verse 7 where God says to Samuel, "Do not look on his appearance or on the height of his stature, because I have rejected him. For the LORD sees not as man sees: man looks on the outward appearance, but the LORD looks on the heart."
Man, how we need this! God looks at us from the inside out. How freeing this is! At best externals are neutral to God. Our body shape, hair color, grades, athletic ability, accent, and job simply do not matter in God's analysis of us. They're not right or wrong, good or bad, they are simply neutral. I don't know about you, but I need this freedom. There are so many externals I can't control and really get tired of trying to perfect. God says, "No problem. Stop worrying about stuff I care little about."
1 Corinthians 1:26-31 is so helpful for this:
For consider your calling, brothers: not many of you were wise according to worldly standards, not many were powerful, not many were of noble birth. But God chose what is foolish in the world to shame the wise; God chose what is weak in the world to shame the strong; God chose what is low and despised in the world, even things that are not, to bring to nothing things that are, so that no human being might boast in the presence of God. And because of him you are in Christ Jesus, who became to us wisdom from God, righteousness and sanctification and redemption, so that, as it is written, “Let the one who boasts, boast in the Lord.” (ESV)
Jesus becomes to us everything we need in order to have a relationship with God and to be found beautiful and worthy by him. David understood this. Sure, Jesus had not yet been revealed to him, but David understood that the one thing that mattered most was developing himself from the inside out. This is why he was chosen by God to be the future king of Israel. Above all else, David was a man after God's own heart (1 Samuel 13:14).