Hard work pays off and when it doesn't that's the moment to work harder.
I really like this line. I think I've seen/heard similar sentiments before. Something along the lines of, if it isn't working, then one isn't working hard enough. I do agree that hard work pays off. People just usually stop before they can see the fruits of their labor.
Hard work needs to be accompanied by other things because working hard in the wrong directions is wasteful. But, if the right things are being done enough of the time a person has a great chance to find growth, gain and development and those things have a way of compounding.