Motivation is a fickle thing. It's all well and good on the first day when you're feeling lit up, but the true gut check is on day 3 or 4 or 105. Cold, hunger, and adversity are going to sap your motivation. It is better to cultivate discipline than relying on motivation. It takes discipline to hit the books on days when all you want to do is stay in bed, curled up under the covers. It takes discipline to hit the gym when you'd rather snack on that 4th slice of pizza. It takes discipline to hit the simulator and fly additional approaches when you'd rather be playing video games or watching TV.
There are going to be days when we get discouraged. We are going to face adversity from outside factors and from our own self-doubt. It is important to remember why we fly and never let a set back get in the way of our goals. Stay on the path. Talk with and support your wingmen and never, ever quit.