Motivation is a thought, a realizable dream, a potent desire to do something because of some reason. It is NOT the act or action itself. Having just motivation is not enough. Being motivated is a good start.
Discipline is when you act on the dream and make it a reality. Discipline is when you take concrete steps to realize the thought or the dream. Discipline over time becomes a habit.
Great entrepreneurs have discipline as a key strength – they take an idea to fruition, or create a successful business.
Success = Motivation + Discipline + risk management
Discipline is what makes motivation happen. Say for example, one is motivated to join the gym but nothing happens unless you get to the gym regularly to push your body around which is where discipline is needed.