'Shark Tank' investor Lori Greiner shares the best advice she's ever received

"Shark Tank" investor Lori Greiner started with a single invention, an earring holder, in 1997 and grew it into a multimillion-dollar family of businesses with products on QVC and in the world's biggest retailers.

On her path to more than 400 inventions and 120 patents, she tells Business Insider that she constantly reminded herself of the advice that both her father and her husband gave: "Don't let business get personal. It's just business. Shrug it off."

It's something she's regularly told the many entrepreneurs she works with.

At the start of her career, Greiner writes in her book "Invent It, Sell It, Bank It!," she had a meeting with a patent lawyer who didn't take her seriously, but she quickly found a way to keep him from impeding her progress.

It was the mid-'90s and Greiner had just paid $5,000 to file her first patent for an earring organizer. The money had come from savings she shared with her husband Dan, so he accompanied her in a meeting with the attorney.

The lawyer spoke exclusively to Dan, even though he sat off to the side as an observer. After 10 minutes of this, Greiner told the lawyer she was done with the rude way he was treating her and that he needed to find one of the firm's partners and have them send in a female attorney. The lawyer who replaced him was Natalie Kadievitch, who has worked with Greiner ever since.

Greiner writes that it's important to call out injustices, "but be polite even as you do it."

She explains:

My entrepreneurs will say, "Aw, that person was a jerk," or, "I can't believe they did that."

And I say, "You know what? Make it work."

Be as charming and as passionate as you would be if they weren't a jerk. Get the sale. Get what you need. And then laugh your way to the bank.

If you let them upset you or they get under your skin, you have just stopped. You've halted progress.

As you develop your career or business, there will be plenty of people who do not think you are worthy of their time or respect, Greiner writes in her book. Although it can be easy to feel vulnerable when you're starting out, you can't let other people's negativity compromise your drive.

"Your success will have everything to do with how you perceive yourself, because how you perceive yourself is how others will perceive you, too," she writes.