God addressed Moses, saying, "I am God. Tell Pharaoh king of Egypt everything I say to you." And Moses answered, "Look at me. I stutter. Why would Pharaoh listen to me?" Exodus 6:29-30 (MSG)
If find it interesting that Moses has been unpacking his whole "I stutter" excuse for three chapters running (who knows how many months or years these chapters cover). It's a great picture of how doggedly we like to cling to our hang ups, insecurities, issues and excuses.
Growth doesn't always happen overnight. Despite our fantasies to the contrary, God does not typically transform people instantaneously in to spiritual superheroes. We don't get bit by a supernatural spider and suddenly become Godly-man. Even the "superheroes" wie think of in the Bible were transformed over time (and the maturity process never stopped). We see Moses "in process" through these early chapters of Exodus, but there are others.
David killed Goliath in an instant, but how many years did he spend alone in the desert with his sheep, learning to use his sling against predators? Saul had a "Damascus Road" experience, but we forget about the years he spent studying and growing before his ministry started. The apostles stood boldly in the face of persecution, but before that they spent three years scratching their heads, fighting amonst themselves, and even denying that they even knew Jesus.
Like any journey, there are times we'd much rather just "arrive" at the destination. However, even those we consider spiritual giants had to grow into their sandals.