The most self-disciplined ...

The most self-disciplined people in the world aren't born with it, but at one point they start to think differently about self discipline. Easy, short-term choices lead to different long-term consequences. Difficult short-term choices lead to easy long-term consequences. What we thought was the easy way led to a much more difficult life. I think that motivation is sort of like a unicorn that people chance like a magic pill that will make them suddenly want to work hard. It's not out there.
 Rory Vaden

Quotes from the same author

The reason we don't get what we want isn't because we don't have the ability or time. We aren't willing to do the things we need to do when we don't feel like doing them. There's an impact of that entitlement on their business. The attitude is you learn to fall in love with the daily grind.
 Rory Vaden
A lot of "successful" people are tragedies, because what they've accomplished aren't the things they wanted. Intentionally create the question "how" instead of accidentally relenting to the question of "should." If I'm not intentionally choosing a good attitude, I'm almost always unintentionally choosing a negative one.
 Rory Vaden
Fear is a big reason. Ultra achievers don't have an attitude for overcoming fear. They just do it anyway, because they're okay with being afraid. Instead of putting energy into reducing fear, they confront it with action.
 Rory Vaden