If you haven't met the real "Mr. Wonderful," you're missing out. Kevin O'Leary is one of the most intelligent, gracious and helpful entrepreneurs I've worked with. You'll get one of the biggest favors if he gives you direct feedback of what he thinks about your business idea. He'll let you know if your idea is gold, it won't work, it needs tweaking, or you should give up.

On screen, he won't tell you something nice to save your feelings. His tell-it-like-it-is approach gained him the nickname "Mr. Wonderful" on Shark Tank, but that isn't all he knows and that isn't the way he is in real life

After 30 years of building businesses, keynote speaker and entrepreneur celebrity Kevin O'Leary knows what works and what doesn't for starting a business. His intuition rarely leads him astray. After chatting with him in New York this May and listening to his advice in various interviews, here are seven things you should know about life and money for startup success.

1. Know how to execute.

O'Leary has met thousands of entrepreneurs and heard all their pitches. What separates those with a great vision from those with great success is execution. "Vision is easy; execution is hard," O'Leary told CNBC co-anchor Tyler Mathisen. These entrepreneurs know how to take an idea, set goals, take action, and learn from mistakes. The rest are just dreamers. 

2. Know your weaknesses.

O'Leary said, "If you're a leader and say you have no weakness, you're full of crap." The best businesses have leaders who know their weaknesses and build teams to augment the areas where they are weak.

3. Know it will be hard work.

Don't become an entrepreneur if you don't want to work hard and sacrifice. Due to global competition, you have to be able to work "25 hours a day, eight days a week," he told Bryan Elliott of Behind the Brand, while giving up time with your friends, family, and yourself in order to build your business. If you aren't willing to sacrifice for success, you'll be out of business because someone else will.

4. Know when it isn't working.

The best entrepreneurs fail a number of times before succeeding. If you aren't making money after three years, you have a hobby--not a business, O'Leary told Inc. You must get your customer acquisition costs below their lifetime value or your business will never make enough money to survive. You'll blow it all on advertising.

5. Know your life partner.

When it comes to choosing a life partner, you have to choose someone who understands the entrepreneur life, he told Inc. Being an entrepreneur means sacrificing your personal life in the short term (which may be years and years) before having freedom in the long term. If your significant other, fiancee, or spouse doesn't understand your drive and motivation, find another one.

6. Know your reason.

If you go into business with the main goal of making money, you will not succeed. "The whole reason to be an entrepreneur is the pursuit of freedom," O'Leary told me. Making money is the derivative of your desire to be in control of your own destiny. Freedom should always be the goal.

7. Know how to spend money.

If you want to make money in the long term, don't spend money on crap in the short term. Don't purchase $2.50 coffees, pay $20,000 for wedding dresses, or buy brand new cars, Instead, "Save your money, invest it, and later you can take everybody out for a great time on the interest you're making off your bonds and the dividends your stocks are paying," O'Leary told CNBC Make it.

O'Leary is a good human, great business person, and a money mentor to millions. He walks the talk by making coffee at home, working long hours, and investing wisely. If you get one thing from his take on money, it should be this: spend little and invest the rest in your business.