I often say to my son, “You gotta do what you have to do, before you can do what you want to do.”
Now, I am usually referring to him doing his homework or chores so he can play with his friends. But I am, in a simple way, training him with some sort of work ethic for mundane task and stating the facts of life that nothing is given.
Everything is earned in one way or another. He might as well learn that now with simple day-to-day routines, because I know in the long run it will translate over into other areas of his life.
You can apply this mantra to any part of life where you need to create some self-discipline. There are things you have to do in order to get the things you want.
Eat. Work. Sleep. Repeat.
Every single human does this daily. But not every person does this the same way. The amount, the time, and the quality of each step shapes pretty much everything we do in our daily lives, as well as our energy level, productivity and our body composition.