This quote means that success is not just possible, but actually achieved. Potential for success is a great thing to have, but it is not enough. In order to achieve success, one must take action and work hard. To use an example, any piece of land has the potential to become a palace, but unless someone takes the time and effort to actually build the palace, then it will never happen. In the same way, potential for success is not enough on its own – one must take action and be successful in order to achieve success.