You to work both smart and hard. People who get rich on their own have to work harder than most, but hard work is not enough. You have to be smart about what you spend your time doing; if something is not moving you forward, you have to be willing to let it go and try something else.
You also have to reinvest your money as you make it. Supposedly Albert Einstein called compound interest the "most powerful force in the universe". Whether he really said it or not, it's very true. In order to get rich you need to avoid paying compound interest, and instead be collecting it on your money.
Another important thing that many self-made wealthy people give credit to is personal connections. Surrounding yourself with people who are supportive, genuinely willing to help you, and who believe in you makes it much more likely that you will stay on track.