When I was 22 years old, I was laid off from my first job as a political reporter. Journalists these days might half-expect such a fate – our ranks have been decimated over the past two decades – but back then, I was completely stunned.

I hadn’t seen it coming, and I had no Plan B.

I woke up the next morning and figured I’d start looking for a job. But when I turned on the news, I realized that wasn’t going to happen. I had been laid off on Monday, September 10th, 2001. That next morning, my employment status was the least of anybody’s problems.

That experience showed me how precarious our professional lives can be. I vowed that I wouldn’t allow myself to be in such a risky situation again, and as a result, I’ve become a strong believer that everyone – even if you have a day job you love and never want to leave – should develop a ‘portfolio career’ with at least one side income stream.

As I argue in my new book Entrepreneurial You, when you develop new income streams – from coaching, consulting, blogging, or a million other possibilities – it not only provides a hedge against economic uncertainty. It also teaches you new skills, brings in additional revenue, and opens up transformative new experiences.

One of my favorite case studies in the book is Lenny Achan, who began his career as a hospital nurse and ended up becoming the head of communications for his hospital system – a very unlikely career progression. What got him there was something he did on his own time, on nights and weekends.

He had become fascinated with smartphone apps, and learned how to develop them. When his boss found out and called him in for a chat, Lenny was initially worried: had he violated some policy he wasn’t aware of? Did they think he was messing around on company time?

But on the contrary, his boss was impressed with Lenny’s initiative, and asked him to run social media for the hospital. Lenny did a great job and was ultimately handed the entire communications portfolio. That dramatic career progression never would have been possible without Lenny developing an entrepreneurial side venture.

Similarly, Bozi Dar is a successful life sciences marketing executive with an entrepreneurial streak. Like Lenny, he also tried to develop a smartphone app – though his failed. It’s important to note that not every side venture is a success.

But Bozi feels the knowledge he gained was invaluable. First, he was able to apply what he learned to create a second offering – this time, an online course – that has been far more successful, bringing in $25,000 in its first year alone. And the skills he’s gained have benefited him in his day job.

Having a background in “technology and digital is highly desirable,” he says. “It enabled me to completely reinvent myself.” He considers himself an “intrapreneur,” innovating inside his company – a perfect combination of professional stability and exploration.

We often see entrepreneurship and working inside a company as diametrically opposed choices. But in the modern economy, they can also be complimentary. When you develop an entrepreneurial side venture for yourself, you create new professional opportunities that are impossible to foresee. In an uncertain world, you’re future-proofing your career.

Dorie Clark is the author of the new book Entrepreneurial You. Her past books include Reinventing You and Stand Out, which was named the #1 Leadership Book of 2015 by Inc. magazine. She teaches for Duke University’s Fuqua School of Business, and you can download her free Entrepreneurial You self-assessment workbook