Robin Chase, the co-founder and former CEO of car-sharing giant Zipcar, learned the danger of hubris the hard way.

"The most important thing to succeeding is intellectual honesty," Chase reflected, speaking at The Next Web Conference in Brooklyn on Wednesday. The event gathered thousands of entrepreneurs, executives, and investors to discuss the future of the Internet, the sharing-economy, and more.

"If you're not honest with yourself about what the reality [of the market] is, you will fail," Chase added.

Founded in 2000, Zipcar grew to a lofty $1.2 billion valuation during its 2011 public debut, and ultimately sold itself to Avis for $491 million. The company began with a single car parked outside of Chase's Massachusetts home -- and a set of keys hidden under a pillow on the front porch. (Keep in mind that this was prior to the advent of smartphones, and back when only around 41% of people in the U.S. could access the Internet.) At the time, Chase and her co-founder, Antje Danielson, had managed to scare up $75,000 of capital to get their concept of "wheels when you want them" -- borrowed from successful European car-sharing models -- off the ground.

About two thirds of that money went into engineering; the remaining $25,000 went to what Chase now refers to as a "stupid product." The idea, she explained, was for a keypad to be placed in the rented car, that would let customers enter their personal information, and report on the condition of the vehicle. Unfortunately, the installation and upkeep of the pads proved far too complicated and expensive to justify.

"We pulled it after three weeks," Chase remembers, which ultimately led the company to come up with its signature key cards. Her biggest piece of advice to business owners: "Do not drink your own Kool-aid," she said. "When something is wrong, fix it."

She likens a young startup to a defunct hotel, or, in a more lurid simile, a "blind mole rate." "Outside you exhibit yourself as this spectacular website, but you know in your heart that behind the scenes, you're this dirty, crummy pathetic little thing," humored Chase.

And she's right: as important as it is to believe in your idea, it's equally important that you approach new challenges and opportunities with a sense of humility.