I'm embarrassed to admit this now, but when I was a kid, I got in a lot of fights. I was voted "toughest" in my school. I would fight any kid who said they could beat me. I wasn't the biggest, but no matter how many times I got hit, I refused to stay down. I was obsessed with Rocky; something in me felt like the underdog who had to prove he deserved a shot at the title.

Now that I'm an adult, I don't get into fights anymore -- but I still have that fire inside. It's the main reason my company is here today.

Soon after my co-founder and I started Tile, we applied to Y Combinator, which mentors founders and gives them seed capital. We got invited to interview in November 2012. I quit my job as an engineer, and the next week I drove from my home in Santa Barbara, California, to San Francisco, where Y Combinator and my partner were both based.

The pitch was a disaster. They asked a lot of questions we couldn't answer. We got a prompt rejection letter that night.

I drove home the next morning feeling crushed. These guys know what they're doing. If they don't think it's a good idea, maybe it isn't. I had another job offer, maybe I should take it.

Over that six-hour car ride, my mood changed. The fighter got up. They didn't see what I saw? I'll make them believe. I didn't need to quit; I needed to work harder.

When I got home, I told my wife, Camila, what happened and we talked about what to do. She still believed in the idea, and in me. We had four months of cash saved. I had until April 1 to show signs of life.

I spent most of my waking hours over the next six weeks building a new prototype. It was done by New Year's -- but it only worked 30 percent of the time. In January, we pitched Tandem's investment group. We lucked out and the demo worked. Tandem put $200,000 into Tile in February, and we had our proof of life.

That spring, we hunted for manufacturers. We got rejected by at least a dozen shops. No one wanted to take the risk: We had barely any money and no customers.

No way I was giving up now. We did a crowdfunding campaign to test the market. We needed at least $20,000 in pre-sales. We reverse engineered successful campaigns and copied their playbooks. We made a video and launched in June.

In one month, 49,000 people ordered $2.68 million worth of Tiles. Now we needed to find a bigger manufacturer that could make half a million Tiles to fulfill those orders, plus more to sell online. The campaign was all the proof they needed.

In 2015 we started pitching retailers. I was set on Target: a mass-market retailer that could get Tile into the hands of millions. They weren't sold. We weren't a big enough brand. But they threw us a bone: Target was about to open a small, experimental storefront in San Francisco that would showcase cutting-edge technology for the home. They would let the people decide if Tile was Target-worthy.

To everyone's surprise, our little device was their best seller. Target said we would be on their shelves in October in time for the holidays. I'm proud to say we're still in Target and they're a terrific partner.

Time after time, I've had to prove that my company deserved a chance. If I listened to people who told me "No," I would still be dreaming of where I am now.

My advice to all entrepreneurs is to never, ever stay down. Get back up. Over and over again.