This story is part of the Behind the Desk series, where CNBC Make It gets personal with successful business executives to find out everything from how they got to where they are to what makes them get out of bed in the morning to their daily routines

As far as career accomplishments go, it's hard to top Eric Schmidt.

A self-described software "nerd" from Falls Church, Virginia, Schmidt was hired as Google's chairman and later CEO by co-founders Larry Page and Sergey Brin in 2001 to provide some "adult supervision" to their growing web-search engine. At the time, Schmidt was only 46 years old — but already an experienced tech executive, with top positions at Novell and Sun Microsystems on his resume.

He served as Google's CEO until 2011, helping transform the company from a young Silicon Valley start-up into a global tech behemoth with a market value today of more than $1.8 trillion. He stayed on as executive chairman until 2017, and technical advisor until 2020.

Currently, Schmidt is the world's 66th-richest person with a net worth of around $23 billion, according to Forbes — so it's easy to forget how small Google was when he arrived on the scene.

"The company was 100 people, and I didn't particularly believe in the advertising model," Schmidt, 66, tells CNBC Make It. Even as CEO, he says, he had no clue how much Google could grow: "I just really liked the people."

Instead of pushing some grand plan to turn the start-up into a giant, he says, he focused on his own individual strengths — being a workaholic, having a passion for building things and leaning into his own likeability. That last trait, he says, caused people to underestimate him at times.

"I always benefited from the presumption that I was a nice guy, and not a very good businessman. So my schtick was: I was always the nicest person in the room," Schmidt says, adding that if you use that strategy, "you'd better be capable of backing it up with real rigor, real outcome and real decision making."

In terms of Google, the rest is history. Today, Schmidt is focused on his philanthropic initiative Schmidt Futures, which supports big-idea research in fields like artificial intelligence, biology and energy. Last year, he co-wrote the book, "The Age of AI," as a roadmap of what the technology's future could look like.

Here, Schmidt discusses building a successful career, working with Steve Jobs, his biggest mistakes at Google and how he handles criticism.

On building a successful career: 'Luck is the first and most important thing that I had'

I think that anyone in my position should start by saying that luck is the first and most important thing I had. Luck of birth, education, interest, timing and the business I was in. I also worked hard, but luck is just as important, if not more important, And as you get luckier, you create your own luck.

I was a young executive, promoted quite quickly. I describe myself as a workaholic. Most people are not workaholics, thank goodness.

The most successful people have a lot of skill, and also grit. I don't think I understood my ambition — I just thought what we were working on was really interesting. But I got my strength as adulthood proceeded.

It took a very long time for me to understand who I was, and what I was good at. It's important to become comfortable about who you are and how you behave and react, because there's so much criticism and pressure today, especially for young people.

How Steve Jobs influenced his leadership style: He 'was not a normal person, by any means'

Steve Jobs, who I worked very closely with [Jobs recruited Schmidt to be on Apple's board from 2006 to 2009] and admired greatly, was not a normal person, by any means.

When he was "on," his charisma and insights were so extraordinarily better than anyone else's that he was able to overcome any handicaps with the way he treated people. People admired him so much.

If you look at history, great leaders have this unique capability to inspire people on a personal basis. The important thing isn't whether you're flappable or low-key, but whether you can inspire people to join in and get excited to change the world.

[Personally], I learned it's important to have teenagers. They're relatively unmanageable, but they need to be managed. You learn to let them do what they want until it gets dangerous or serious. Then, you have to put your foot down. Everything is fine until it's not, in which case, we have to act quickly.

That's a pretty good management style. But I don't want to say there's only one management style.

In building Google into a behemoth: 'We made many mistakes along the way'

I had the benefit of working with Larry [Page] and Sergey [Brin], who were both my best friends and my partners. Larry, Sergey and I would have these huge food fights over this or that. We would honestly disagree. But there was never a moment where I doubted their commitment to the company and the cause.

If the two of them were in agreement, I would usually just say, "yes." If they disagreed, I would force a process where the three of us came to some conclusion. Usually, their ideas were better than mine.

[When I started at Google] I didn't understand the scale of the company, and I had no idea what was possible. I would have been suspicious if you told me [how big Google would get]. In hindsight, I wouldn't change a thing — but we made many mistakes along the way.

I think the biggest mistake I made as CEO was about social media: Google was early in social media, but didn't really execute it very well. The timing of the entry into these about-to-explode platform markets is incredibly important. Even being a few months early makes a huge difference with the right product.

On handling criticism: 'Get used to it. I got used to it'

I'm careful about what I talk about nowadays, because I'm in this interesting class of "tech people" who somehow get criticized for everything we do.

I have to tell you that I didn't encounter the kind of criticism that I've had at Google, before Google. I think part of that is [because] the social media world and the [media] changed and everything became about power and influence.

As a public figure, you learn to let it go. You learn that most of the stuff that's false, people forget. The attention span of our society now is very short.

That criticism comes from a sense of both accomplishment and envy. The fact of the matter is: I think it's part of life. So when I talk to people now, I say, "Get used to it. I got used to it."

This interview has been edited for length and clarity.

Correction: This story has been corrected to reflect that Schmidt Futures is a philanthropic initiative.

Don't miss more from Behind the Desk:

Why the first Black woman CEO in the Fortune 500 says ‘being the minority’ can be a career advantage

How Ellen Ochoa, the first Hispanic woman in space, dealt with 'people who didn't think I should be there'

Designer Vera Wang on starting her company at 40: 'I thought maybe it's just too late for me'

A-Rod Corp CEO Alex Rodriguez on his life and career: 'It's an imperfect story'