Herb Kelleher, the cofounder and longtime CEO of Southwest Airlines, died last month. We lost a great business leader and visionary—a fearless brand builder, through-and-through. Whenever we lose one of the greats, I always wonder what we can learn from them. So here are Five Big Lessons Herb left behind for those of us who try to move brands forward every day.

Lesson #1: Be More Human

Herb was a likeable, approachable, generous, unpretentious man. What you saw is what you got. He treated everyone he met as if he’d known them for years. This authenticity transferred to his brand. Why is Southwest Airlines considered to be so friendly, high-energy and fun? Because Herb was all of those things. Don’t treat the folks who buy from you as “consumers” or your “target audience.” Treat them like real people. Because they are.

Lesson #2: Be Driven by Purpose

Herb famously said, “Market positioning changes. Business strategies change. But purpose does not change.” He believed that Southwest was not in the airline business—it was in the freedom business. Their purpose was to give millions of people “the freedom to fly.” This purpose still permeates everything his company does. It’s not just a slogan. It’s a mantra, a rallying cry, a cause. What does your brand stand for? What purpose drives your company?

Lesson #3: Commit to Simplicity

Herb built the most successful airline ever, not by constantly innovating, but by keeping things simple. The company flew just one kind of plane (the Boeing 737), which made it easier to maintain and repair their fleet, and easier to train pilots. It operated using point-to-point flight routes, avoiding the constant delays of traditional hub-and-spoke systems. No change fees. No baggage fees. No meals served. No assigned seats. Everything was intended to keep things simple. So instead of trying to reinvent your category, maybe you could just simplify it instead. It worked for Herb.

Lesson #4: Your Culture is Your Greatest Asset

Herb didn’t just build a great company, he created a stellar culture. Southwest Airlines is known to be a great place to work. Its employees feel valued and it shows in the service they deliver. It’s famously a casual and loose culture, with many of their flight attendants wearing shorts and polo shirts. Most have a smile on their face and always appear to be having a good time. Even the baggage handlers. This is not common in the industry, to say the least. Want to build a successful company? Start by building a strong culture.

Lesson #5: When in Doubt, Have Fun

The one word most often associated with Southwest Airlines is FUN. Herb made sure of that. Business should be fun. Marketing should be fun. Ad campaigns should be fun. When did everything get so serious? If you have a choice (and you do), choose fun. Herb always did.

As you try to navigate the always unpredictable world of brand-building, keep in mind the lessons that Herb Kelleher left behind. They’ll serve you well.

And if you need help bringing these lessons to life, shoot me an email. We help brands like yours navigate this stuff every day.