To be a good leader you must first be a good follower.  

Your ability to lead is limited by your ability to follow.

So, good leaders were first good followers. When they followed, of course, they had a boss. Maybe that boss was a good leader, maybe not. Regardless, that boss had strengths and weaknesses. That boss' strengths provided opportunities to learn. That boss' weaknesses provided opportunities to use strengths. And so, the good follower watched, listened, and learned and the good follower used personal strengths. Over time, the good follower developed and improved. Over time, the good follower learned what it takes to become a good leader.

To be a good leader you must first be a good follower.  

Your ability to lead is limited by your ability to follow.