I've always said that leadership is a choice. To be more exact, a choice in response to a situation. In every day life, you are constantly faced with choices. To be a leader, you must consistently make choices that put others first, take responsibility for your actions, and treat others with trust and respect.
So in a way, leadership is reactive in nature. Seems counter-intuitive when you think about it. Leadership should, well, lead.
My mother used to always tell me, "it is not what happens, but how you handle it that counts." I don't think I can say it any better than that. You don't lead by telling people what to do. You lead by responding to a crisis in a constructive manner, keeping a cool head and coming up with solutions. You lead by sacrificing yourself for the mission and for the team, setting the example for others to follow. You lead by taking responsibility, enabling others to make suggestions and contribute in other ways. You lead by how you treat others, regardless of provocation, developing a relationship based on trust and respect with others around you; a relationship that translates directly into influence.
And when you are truly in charge, others began to react to you. You react to the situation, others react to you. Your choice on how to react becomes the catalyst for others to act.