We know that Moses was concerned for his people, and had acted before—at great risk to himself—to help Israelites suffering under the yoke of the Egyptians. HIs own people had even derisively asked him, “Who made you a prince or a judge over us?” (Ex. 2:14) The answer of course is that God did. But when God told Moses that, he baulked, saying:
I’m not qualified. (“But Moses said to God, “Who am I, that I should go to Pharaoh, and that I should bring the sons of Israel out of Egypt?” Ex. 3:11)
I can’t answer questions or objections that will come up. (“I shall say to them, ‘The God of your fathers has sent me to you.’ Now they may say to me, ‘What is His name?’ What shall I say to them?” Ex. 3:13)
I don’t think this will work. (“Moses answered and said, “What if they will not believe me, or listen to what I say? For they may say, ‘The LORD has not appeared to you.’” Ex. 4:1)
I don’t have the right skills. (“Please, Lord, I have never been eloquent, neither recently nor in time past, nor since Thou hast spoken to Thy servant; for I am slow of speech and slow of tongue.” Ex. 4:10)
I’d really rather You have somebody else do it. (“But he said, “O my Lord, please send by the hand of whomever else You may send.” Ex. 4:13)
It is amazing the Moses was ever ruler at all—the people disowned him and he tried to get out of it. So was he able to accomplish anythign? Because God said, “Certainly I will be with you.” (Ex. 4:12). That makes all the difference and lets us work by the strength that He supplies. So what has God instructed you to do, and what excuse against it?