Today, Spanx is a household name. That wasn't the case when Sara Blakely, a 25-year-old fax machine saleswoman, had the idea for the product about 20 years ago. Despite the side eye-ing--and sometimes flat-out laughter--about her shapewear concept, Blakely went on to become America's youngest self-made female billionaire. 

Run with it. Ignore what everyone else says. 

Her simple-yet-powerful advice to early-stage entrepreneurs with big ideas? Keep going. Don't let being laughed out of rooms stop you. "If you have an idea, talent, or with it," she posted on LinkedIn

When Blakely first began exploring the idea for footless pantyhose, she didn't tell many people. "Ideas are the most vulnerable in their infancy," she says. But those she did tell were generally not enthusiastic. She heard from several: "If it's such a good idea, why hasn't anyone else thought of it?"

The doubters do you no good. 

But no one else had thought of comfortable, breathable, and footless pantyhose that didn't ride up. Most of the major players in the undergarment industry were dudes. They weren't even their own customers. The products currently on the market were made of thick material, which made it feel like you were wearing workout clothes underneath your regular ones.

Though Blakely didn't have an MBA and was not a designer by trade, Spanx ended up being a million-dollar idea. The company made $4 million in sales in its first year.

Blakley was smart to socialize her idea only to a select few. Otherwise, the naysayers might have talked her into quitting before she even started. She believes that negative self-talk is one of the top barriers that get in the way of entrepreneurs' success. 

What's especially ironic is that years later, those people who thought she was crazy were clambering to be part of the Spanx story. "One day, people who never believed in you will talk about how they met you," Blakely says. ​