My side hustle made $10,000 in a month. It convinced me to leave my law career.

• Greg Smith started tutoring the LSAT in law school.
• He automated a course and out-earned his lawyer salary selling it.
• He grew and scaled a learning platform that now generates $75 million in annual revenue.

This as-told-to essay is based on a conversation with Greg Smith, CEO of Thinkific. It has been edited for length and clarity.

I became interested in corporate law because of the role lawyers play in pivotal business decisions. As a CEO, I might navigate a merger or IPO only once or twice, but as a corporate lawyer, I'd be dealing with them constantly. It seemed to me there were more exciting corporate transactions in a few years of corporate law than there were in two lifetimes of being a CEO.

That pushed me to go to law school. While there, I started tutoring for the LSAT to help pay my bills, including student loan payments. I realized that a lot of my tutoring was repetitive, but I was limited by how many students I could fit into a room. I wanted to reach more people, have more impact, and generate more revenue.

So, in 2005, I launched an automated course. The course started generating thousands of dollars a month, without me investing much time or money. Once, when I had a month of my law job, I really focused on promoting the course, and it generated $10,000 in a month — more than I was making in my corporate role. That was a real signal that I should go deeper with this.

Soon, others asked me to help build their course platforms

I had always been drawn to entrepreneurship — probably because my parents were always thinking about their big ideas, but never able to follow through because of their day jobs. One time, on a plane ride, I had an aha moment: I needed to build a business.

I didn't immediately think about my course. Instead, I left my lawyer job for another startup opportunity, but that didn't pan out.

As I considered my options, I realized that other people and companies were already approaching me about helping them create a platform to support their own educational courses. I had inbound leads, and the solution they were looking for, so I decided to give it a try. In 2012, I founded Thinkific.

My brother was a cofounder, but we often butted heads

My brother Matt, who is eight years younger, saw me struggling to write code. He stepped in to help and became a cofounder. In the early days, there was a fair amount of healthy and unhealthy conflict between us in the office. We were driven and wanted to reach the same place, but we had different ideas about how to get there.

We both wanted to be the CEO — the one making major decisions. But in reality, there weren't that many decisions to be made. After three years of working together, Matt left to pursue another idea. Although we'd had disagreements at work, we always got along well on the weekends.

As Thinkific continued to grow and scale, Matt became one of my most trusted advisors. He briefly rejoined the company as Chief Strategy Officer, and our dynamic was very different. The company was growing so fast that we had tons of decisions to make, and I was grateful for anything he could take off my plate. Today, he's an advisor to the board. He's also the guy I can call when I'm struggling, just to talk.

I teach my kids to be proud of their failures

My kids are 7 and 10, and I talk to them a lot about failure. When my daughter was about 3, she asked what failure was. I told her that when something doesn't go the way you want, it's a huge opportunity.

Now, I'll regularly ask the kids about the things they failed at, to show them they should be proud of their failures. They love talking about it so much that they'll tell other kids, "You failed!" like it's the most exciting thing. Sometimes other parents give me the side eye about that, but I'm glad that their approach to failure is healthy — that will help them when they're trying new things.