Whether she's deciding to invest in an entrepreneur's company or interviewing someone for a job, Barbara Corcoran looks for one key personality trait. 

Do they have a good attitude? "You couple a strong work ethic with a positive attitude and you'll get a winner that you can do something with," she writes on LinkedIn

Hiring for positivity.

Someone who is already unhappy will bring bad energy to their work. Unhappy people don't just bring themselves down. They bring everyone else down, too. Corcoran's not interested in hiring them.

It doesn't matter how impressive someone's background is. That's why she doesn't even look at a candidate's résumé until after the interview. 

To help hire for positivity, Corcoran always leads with one open-ended interview question: Tell me about your family. "If talking about their family couldn't give them a positive attitude, there's nothing I can do that's going to change it," she said. 

It's not about having a happy family. 

This doesn't mean that Corcoran exclusively hires people who have happy families or picture-perfect childhoods. She wants to learn how you describe your life experience. Are you a positive person despite encountering adversity? Or are you someone who complains about the bad cards you were dealt?

Even if you had a less-than-ideal family situation, how you choose to answer this question is telling. One commenter, Joy Alvey, explained how she would go about it. "I would simply say something like, 'I struggled to have a great relationship with my parents, but that has made me focus on having the kind of relationship I always wanted with my own children.' "

No one is 'born' happy. 

Happiness isn't ingrained in your DNA. Dr. Laurie Santos, psychology professor at Yale, teaches a wildly popular course on happiness. She points to research that proves that many of our assumptions about happy people are dead wrong. 

She acknowledges that there's a slight genetic component to happiness, but it's much less smaller than we think. Happiness is not fixed. Really, it's up to us to improve our own happiness. 

According to the research cited by Santos, we become happier by taking small intentional steps towards it. Daily actions like keeping a gratitude journal, interacting with strangers, and slowing down to observe joyful moments are all effective at boosting happiness and well-being. ​