Sure, your company has a board of directors, but shouldn't you have your very own board of directors too? Yes, absolutely, says Square CFO Sarah Friar.

"It's a very fancy term for the idea of thinking broadly about who your mentors are, who your role models are going to be in life," Friar said Thursday to group of mostly aspiring founders at the Women 2.0 conference in San Francisco. 

Friar came to the five-year-old mobile payment company Square in 2012. Previously she had been with Goldman Sachs managing a business unit for about a decade. Now she is virtually head of risk for a startup that's aiming to push the limits of commerce. 

"Adrenaline is usually the terror that I feel when the next great idea comes from one of my engineers or from Jack," Friar said, referring to Square CEO Jack Dorsey. She indicated that that fear is why she now loves her day job.  

But the transition to an entrepreneurial environment wasn't easy. She acknowledges that members of her "board of directors" each in their own way helped her to move from a comfortable job at Goldman to the fast-paced, epinephrine-fueled startup life. Here are her four recommended types of mentors:

Someone You Work With

Friar said it's great to have a colleague who is also a role model. They'll point out what you do well, but more importantly, they'll be honest with you about what you need to do better.  

Someone You Aspire to Be 

Back in Friar's days with Goldman Sachs, she looked up to Salesforce CEO Marc Benioff, with whom she worked every once in a while. "I was thinking, 'Marc Benioff's not going to be my mentor,'" she said. "But I decided I would kind of stalk him into it. I kept emailing him, asking him questions. And it really paid off -- to that day I decided I did want to change careers." She called Benioff up, and it led to a stint with Salesforce just before she joined Square.

A Mentor From a Previous Life 

Ex-CFO of Goldman David Vernier is literally on Friar's board of directors at Square. Personally, though, she especially values his advice because she used to work with him in her former life. "I find his advice and his mentorship today even more interesting because he's seen me in different guises in my career," Friar said.  

A Person Who Isn't Senior to You 

Lastly, you don't necessarily need to look up to a senior person to be your mentor. Friar said you're just as likely to learn from the people all around you. 

"I put my kids on here because I love the fact that they teach me to not be constrained in how I think about things," Friar said."My daughter when you ask her what she's going to be when she grows up, she says, 'Well I'm going to be an Olympic athlete, probably a gymnast, also going to be an inventor, and I'm going to be a professional artist.'"