Editor's note: We asked noted entrepreneurs to reflect on what they wish they'd known starting out. Barbara Corcoran is a real-estate mogul and celebrity investor on Shark Tank.

Barbara Corcoran got straight D's in high school and college, and held 20 jobs before the age of 23. In 1973, she borrowed $1,000 from her then-boyfriend to start a real-estate empire.

She kept her business alive through the stock market crash of 1987 by mortgaging her country home, selling her one-bedroom co-op, and teaching real estate courses at New York University. Corcoran eventually sold her company to the real estate behemoth NRT for $66 million in September 2001--two days before the terrorist attacks. In 2009, she first appeared on ABC's Shark Tank, where she continues to make deals with entrepreneurs.

Here, the real-estate mogul and celebrity investor reflects on the skills and lessons she wishes she knew as a young entrepreneur.

On the importance of staying the course...

Staying in the game no matter what crap is hitting you against the head. I learned that if you hang around after your worst failures, there's always a prize for you. A lot of people--and I've invested in a lot of entrepreneurs--make the mistake of thinking, 'this is just terrible.' But something good always comes if you're just there to catch it.

When you think you're failing, you feel like people are watching you. I learned to be very free of that concern early on because I found that nobody is watching, nobody gives a damn, and all they care about is themselves. That's the truth in business. Once you're free of that, it's a great opportunity to let that go and keep doing what you're doing.

On discovering what you do well--and truly sticking to it...

I would always give someone advice along the lines of play up what you do well versus a criticism of what you're not doing well. If you focus too much on what you think your strengths are and do more of that, it always works because people always do well at what they naturally do well versus trying to be everything to everybody.

Nobody is Superman or Superwoman. Everybody has a certain skill set that they excel at and it usually matches their personality. So I think figuring out your personality and what you do well and sticking with that is really important.

On looking fear in the face and taking the leap...

The hardest lesson you always learn, I think, is that you're more capable then you think you are. It's when you shy away from stuff because you think you can't do it, or that the results are going to be likely bad. If you've got that dream in your head, you better go for it before you have the wife, three kids and a mortgage. Or the husband, who's finding himself and even without kids, life gets in the way. So the rush to go and do it when you're young is very important. Because you have the great advantage of being young of having no fear.

On the dangers of negative self-talk...

Try not to listen to the negative self-talk inside your head. You're going to get that from the outside, your competitors are going to beat you up and spit you out. That's the real poison I battled with it early. My negative self-talk was saying things like, "you shouldn't have done that," or "they're making fun of you," or "you don't belong here."

That kind of stuff is like a leak in your gas tank. I've learned to replace it with a new thing, my little tape goes like, 'Screw you, I'm going to be rich, I have just as much right to be here as the old boys sitting here. I could be your competitor and beat you too. I start when I feel myself being like Alice in Wonderland sliding down that little rabbit hole with the self-talk.

On the 1 advice that would have inspired her early on...

It would have been helpful for me to see that there were a lot of people successful in life that couldn't read, couldn't write...and yet, many of them were billionaires. I had to discover that little by little as I built my own world successfully. It would have been useful to see that you don't define someone's intelligence as we do in a school system. It's a cruel thing that sadly makes so many kids feel like they'll never be successful.