In 2018, I interviewed leaders from a variety of fields for my "Office Hours" podcast. It was the podcast's best year yet, with guests ranging from NFL star Russell Wilson to Microsoft CEO Satya Nadella. As I look ahead to 2019, here are some of the most impactful leadership lessons I learned this year.

Revisit founding principles

Satya Nadella and I spoke about refreshing the company culture of a 43-year-old household name: Microsoft. After Microsoft fulfilled its initial mission -- a PC in every home running its software -- the company faced an identity crisis. What was the next mountain to climb?

Satya turned to the history of the company for inspiration. Its first product was an interpreter to the BASIC programming language, which made computing more accessible to hobbyists. In other words, it enabled them to do more.

By returning to first principles, Satya realized that the true mission of Microsoft wasn't about a computer on every desk -- it was about empowering people and organizations to achieve more. This led to bold moves: launching Microsoft Office on Apple's competing iOS platform and adding support for Linux, two arch rivals of Microsoft, both of which have paid off. Microsoft has added $500 billion+ in market cap since Satya took over as CEO in 2014, which is incredible. Satya reminded me that there's power in returning to the founding principles of your company, especially when you need to "hit refresh."

Great leaders are self-aware.

Seattle Seahawks quarterback Russell Wilson emphasized that a motivated team starts with a self-aware leader. Leaders need to harness their own mental toughness, staying focused on the vision and outlining the steps to get there. It's about remaining Zen under pressure and focusing on what you can control.

While Russell's and my day-to-day roles are very different, we face similar challenges as leaders. We're both responsible for the motivation and performance of our teams -- and we both want to win. Russell reminded me that my own mindset and how I communicate the vision are just as important as the tactical choices we make on the field or in the office. 

Give permission to disengage.

A leader can't always be "on," nor can your employees. Arianna Huffington discussed the importance of disconnecting and giving your employees permission to do the same. "Stress and burnout have become global epidemics wherever you are in the world," she said to me. "It is unnecessary suffering."

Leaders have a responsibility to encourage downtime through benefits, policies and individual actions. As leaders, we set the tone for the culture and expectations of employees. If I'm sending emails late at night, I might be sending a message to my direct reports that they need to be "on" at all hours of the day too. If I never take vacation, my employees won't feel they can either. Downtime prevents burnout, so it's something I'll continue to prioritize in the coming year.

Empathy fuels innovation.

Cindy Eckert is a trailblazer. She's the entrepreneur behind the first FDA-approved drug to treat low sexual desire in women, and she's built two businesses from the ground up. My conversation with Cindy reinforced a deeply held belief of mine -- that empathy drives innovation.

When Cindy started her career, she saw something she couldn't reconcile. Despite a ton of scientific research, not one sexual-health drug for women existed on the market. This wasn't a research problem; it was an empathy problem. When we're unaware of or can't relate to a population's experience, companies and entire industries stagnate. A diverse set of people in positions of power is critical to fostering empathy. As leaders, we need to double down on diversity efforts in 2019; it's the right thing to do, and it's one of the keys to building an innovative company.

Focus on equity and belonging.

Lastly, I enjoyed my conversations with CNN's Van Jones and Bloomberg journalist and "Brotopia" author, Emily Chang. Both have a lot to teach leaders about creating cultures that empower and include people from underrepresented communities.

Van said something that really stood out to me: "Genius is uniformly spread out, but opportunity is not." As leaders, we need to tap into genius everywhere by managing our own biases and expanding where we look for talent. Emily reminded me that once people are in the door, you have to make sure that they're engaged and feel they belong. Establishing employee resource groups and starting company-wide candid conversations to bring everyone into the dialogue is a great step in that direction. But there's more work all of us can do.

Learning from other leaders is one of the most valuable ways to spend your time, and you don't need a podcast to do it. This coming year, connect with people you admire -- you'll be a better leader for it. I'm excited to continue to learn from more great leaders in 2019 and beyond.

Correction: An earlier version of this article misstated Cindy Eckert's last name.