Starting and operating a business just might be the most challenging and stressful thing you ever do.

You know what else it is? Satisfying. Gratifying. Totally fulfilling. Incredibly rewarding.

But not all entrepreneurs are happy with themselves, their businesses, and their success.

The definition of happiness is completely subjective and differs from person to person, but there are common themes and traits among the ultra-successful--and much to be learned from them!

Check out these quotes about happiness from 16 entrepreneurial superstars:

  1. If you want to be happy, set a goal that commands your thoughts, liberates your energy, and inspires your hopes. --Andrew Carnegie
  2. I'm convinced that about half of what separates the successful entrepreneurs from the nonsuccessful entrepreneurs is perseverance. --Steve Jobs
  3. You must fall in love with what you do, because being an entrepreneur is a lot of hard work, and overcoming a lot of adversity. From that love will come the dedication that will get you out of bed at 4 a.m. because of a great idea you just had and get you to work till 11 p.m. and not feel tired. --Ken Field
  4. If you want to be an entrepreneur, it's not a job, it's a lifestyle. It defines you. Forget about vacations, about going home at 6 p.m.--last thing at night you'll send emails, first thing in the morning you'll read emails, and you'll wake up in the middle of the night. But it's hugely rewarding as you're fulfilling something for yourself. --Niklas Zennstrom
  5. I want to represent the idea that you really can make what you want ... I believe I can create whatever I want to create. --Will Smith
  6. When everything seems to be going against you, remember that the airplane takes off against the wind, not with it. --Henry Ford
  7. We've been looking a lot at the health of our people, and making sure we're helping them stay healthy and quit smoking. Our health care costs have grown a lot less fast than other companies' as a result of that. But our people have also been a lot happier and more productive, which is much more important. --Larry Page
  8. It's not how much money we make that ultimately makes us happy between 9 and 5. It's whether or not our work fulfills us. Being a teacher is meaningful. --Malcolm Gladwell
  9. One of the huge mistakes people make is that they try to force an interest on themselves. You don't choose your passions; your passions choose you. --Jeff Bezos
  10. I want to be happy. I realized that being happy isn't necessarily about getting there; it's how you get there. It almost sounds like a cliché, but every entrepreneur I've talked to--every good entrepreneur--really enjoys the "how you get here." --Ben Huh
  11. Don't buy into the 20-hours-a-day entrepreneur myth. You need to sleep 8 hours a day to have a focused mind. --James Altucher
  12. I like to be involved in things that change the world. --Elon Musk
  13. I don't consider myself a social entrepreneur, but I'm thrilled to be doing good, if that's what I'm doing. --Perry Chen
  14. I've always been an entrepreneur, but it's never been about the money. I like a challenge, the harder the better. --Terry McAuliffe
  15. You can't be an entrepreneur for other people. You can't start a company for other people. You have to love it more than you ever thought of loving something that wasn't a human being. The demands will kick you down and rob your life--but yet, it is so rewarding. --Blake Lively
  16. I advise all of the entrepreneurs that I know to attend at least one entrepreneurship event every week. The worst thing an entrepreneur can do is to confine his or herself to a cubbyhole. --Vivek Wadhwa