Dave Ramsey is the New York Times best-selling author of Financial Peace Revisited, The Total Money Makeover and More than Enough. In his most recent book, EntreLeadership, he opened his championship playbook to give readers the keys to business success.

I’ve been in business a long time. I’ve read just about every leadership book on the market, and I’ve attended every seminar worth going to. I’ve learned every tip and trick there is to know about building and growing a business. With all that wealth of information, do you know where I learned the most important business principle? It was Sunday School.

I firmly believe that the single-most important business principle—one of the cornerstones of our success—is the Golden Rule: Treat other people the way you’d want to be treated. Like a lot of the stuff I teach, this is pretty easy to understand; it’s just hard to actually do.

If you run a company or lead a team, your business is people. Whether it’s your team members, customers, vendors, neighbors or even your competitors—every individual around you is unique and uniquely important. They all have hopes and dreams. They all have fears and struggles. They all have incredible successes, and they all have mind-blowing dysfunctions. They are all people, and every single one deserves to be treated with respect, dignity, and a caring heart.

In his book, Thou Shall Prosper, my friend, Rabbi Daniel Lapin, says God is inordinately pleased when we are obsessively, compulsively consumed with the needs of others. As businesspeople, that’s an easy one to understand as far as our customers go. But do you apply this principle to your own team members? Are you doing what’s best for them?

For example, last year a lady on our team walked into my office with tears in her eyes and said, “My baby is sick. She’s three years old and has cancer.” We gave her all the time off she needed, with pay, to deal with the chemo, and we didn’t count it against her vacation time. Some of our guys cut her yard, and others cooked her meals. Members of the accounting team rallied around her and covered her work while she was out. Why? Because that is how I would want to be treated if my baby was sick. It’s the Golden Rule, right?

Success comes in many, many different forms. For me, it’s not about wealth, how many toys I have, or even what the media writes or says about me. My achievements come from my family, my team members, and the number of lives that have been changed by what we do. It should be the same for you. When you get to the end of your life, what will you look back on and smile about? It won’t be about material things. Stuff doesn’t matter. Accomplishments matter a little bit. But people? People matter most.