Motivation gets you going, discipline keeps you growing. Let me say it this way, motivation is a futile exercise without discipline following it. If you get motivated to do something, but lack discipline to follow through and remain excited, and driven, you will fall flat as soon as the motivation wears off.
On the other hand, if you start with a passion to see a task completed or a goal reached, you will see motivation as momentum increase. Discipline is the bridge from where you are to where you want to go.
So where do you get discipline? It comes from your driving passion. You need to love what you do so much that it does not seem like work. You need to have a belief that you can actually pull it off and you need to know that it is what you are made for. When all of those come together the daily grind that slows most people down will not be a problem.
The road blocks that send people off course, the disasters that overwhelm your hope and the missed goals that keep you feeling like a failure will all fade in the shadow of discipline if you have a passionate belief that you will one day reach your big payoff of significance.
Be a leader. Be an influence. Be significant.