Some argue that no science of success is possible.
The fate of an enterprise or project, the contention goes, is determined by too many variables to be predictable.
In business, there is advertising, word of mouth, the availability of capital, talent, and good old-fashioned luck.
Successful people are not perfect. They are likely to be the first to tell you that. Some might even say they aren’t the luckiest people in the world.
One thing is clear, though. They do not quit.
Here are 10 quotes from 10 people who didn’t give up: