I recently took a long weekend away from work and home to visit my family and while I was away I caught up with my brother for a beer and and a yarn and we got to talking about commitment.
We were both at various stages of completing some pretty major projects in our lives and were discussing how hard it was sometimes to turn motivation into something tangible. In particular we discussed the fact that motivation is always strongest at the beginning of something and then once you move into action it seems to fade away.
Our conclusion was that this is why commitment and discipline are essential to success. Commitment turns motivation into action and discipline makes sure that the initial push that comes from great motivation isn't dissipated by an unsteady course.
Commitment also creates focus and energy and empowers you to stay away from influences that would try to distract you from doing what it is that you really want or wanted to do. It is one of the most powerful principles in our lives. But sometimes we don't take it seriously - in fact many people now even openly disparage it, saying it takes away from independence and freedom. I think it does just the opposite. It makes you free by taking away the competing influences in your life so that you can focus without being tempted to deviate. It gives you freedom to achieve your goals and ambitions to the fullest.
In my opinion there is nothing more needed in order to be successful in anything.