Leadership is taking responsibility for a plan that might fail.
The real weight of leadership is in accepting the risk that comes with it. A leader can never know for sure whether his plan will work, but it is his responsibility to make the best decision he can and pursue the actions he has decided on. This is a heavy responsibility, and it's what makes being a leader hard. It takes courage to be a good leader because it is so easy to attack a leader. True leadership is selfless because it requires that the leader take on a burden for the sake of others.
Most people say that they respect a leader who practices what he preaches, but I think that it takes more bravery for a leader to preach something that they cannot practice. It takes tremendous courage for someone to encourage or tell someone to do something that he has not done themselves. Should a person who has never done drugs tell her friend who is addicted to stop? If she does, she risks being called a hypocrite because surely she has never faced a challenge like her addicted friend is about to face. She does not know how hard it is to quit the drug. But asking her friend to stop is true leadership. True leadership is to say to someone "I know that what you are facing is difficult - I don't even know how difficult because I have never experienced it - but you need to do the right thing - not for my sake but for yours." That is selfless leadership - taking on the risk of criticism for the sake of another.*
This is the most difficult task of leadership (at least for people wired like me): to hold someone to a standard when they don't see why they need to hold to it. I see this challenge all the time in engineering work in classes. The leader knows what will be best for the team, but the team does not know. For example, if there is a design practice (like using an object-oriented coding scheme) that will make a job much easier, but some of the team members don't understand or are too lazy to follow the practice, they might ridicule the leader. A good leader will maintain the standards that he thinks are right in spite of this.
But the catch is that he cannot be 100% sure that his way is the best. It may turn out that his disgruntled employees were correct that they were wasting their time by following the standard. However, to give in to the employees at the beginning of the project is selfish. It is selfish because the leader is only protecting himself. Even though he thinks that following the standard is the best way, he is saying to the employees "Ok, have it your way, you take the blame if it fails" expecting that their way is going to fail all along. A good leader has only one course of action - to make the best (unselfish) decision he can and stick to it even when others do not understand. If he is wrong in the end, he will admit it and bear that burden.
[continue in "cynicism"]
*Of course this does not mean that a leader should be domineering or controlling; there must be a balance. It is not right to hold someone else to one of your personal standards or to any standard if your motive is selfish. This issue is a much larger topic beyond the scope of this post.