David was obviously a good shepherd, maybe one of the best in his area, but he wasn’t ready to be the great king that God wanted him to be. He needed the power of the Holy Spirit to give him the strength and wisdom that was required.
Joshua had an almost impossible task since he had been chosen by God to succeed Moses. Moses had led millions of the Israelites out of captivity in Egypt. During forty years he had led, guided and directed a most difficult nation. Moses had an extraordinarily close relationship with God. How could Joshua possibly succeed this great man? The answer is in Joshua 1:5 ‘As I have been with Moses, so I will be with you, I will never leave you, nor forsake you.
We too are called, maybe not to lead a nation, but called to obedience to God, whatever that will look like for us. Matthew 28:20 gives us the secret for success, ‘So surely I am with you always, to the very end of the age.’