Ronald Reagan was 69 years old when he ran for president in 1980. Despite continual criticism, he won the election and never passed up an opportunity to use humor when referring to his age.

Perhaps the most memorable opportunity came when he was running for reelection four years later. During a televised debate between Reagan and Walter Mondale in 1984, Reagan was asked if he was too old to serve another term. Reagan was prepared and responded in such a way as to quiet his critics. "I'm not going to inject the issue of age into this campaign," Reagan began. "I'm not going to exploit for political gain my opponent's youth and inexperience."

Age is strictly a case of mind over matter. If you don't mind, it doesn't matter.

As I get ready to celebrate yet another birthday, I think about the multitude of lessons that have not only shaped my personal life but have also been integral to my professional journey. Probably the most important one of all: You don't regret most of the things you did; rather you regret the things that you didn't do.

Let me share some of my observations.

Adaptability is essential. Life and business are ever-changing, and being adaptable is crucial to staying relevant and successful. Embracing change rather than resisting it has allowed me to grow and thrive in various circumstances. Stay flexible.

Relationships are priceless. The value of building and maintaining strong relationships cannot be overstated. Whether it's with family, friends, colleagues or clients, investing in relationships pays dividends in countless ways. People do business with those they know, like and trust.

Be in school for a lifetime. No matter how much you think you know, there is always more to learn. The business landscape is always changing. Staying relevant requires ongoing education. Being curious and open to new knowledge keeps you engaged and sharp.

Integrity matters. Honesty and integrity are the cornerstones of trust, and trust is the foundation of all lasting relationships, both personally and professionally. Always strive to be truthful and honorable in your dealings. Your reputation is your most valuable asset.

Listening is a superpower. Good communication is not just about speaking well — it's about listening even better. You can learn more from listening than you can from talking.

Health is wealth. Taking care of your physical and mental health is crucial. As you age, you realize that without health, nothing else is as enjoyable or even possible.

Humor is a lifeline. A good sense of humor can get you through tough times. It is important to take your work seriously, but not yourself.

Giving back. The importance of giving back to the community and helping others cannot be overstated. It is one of the most rewarding aspects of success.

Don't be afraid to take a risk. Taking risks is an essential part of growth and success. If you win, you will be happy. If you lose, you will be wise. By stepping out of your comfort zone, you open yourself up to new opportunities and experiences that can lead to personal and professional growth.

The power of persistence. Success rarely comes overnight. It often requires sustained effort and resilience in the face of setbacks. Stay persistent and don't give up easily. Learn from failures and keep pushing forward. Persistence often separates the successful from the unsuccessful.

Let go of worry. Worry is the most unproductive of all human activities. People get so busy worrying about yesterday or tomorrow; they forget about today. And today is what you have to work with.

Manage your time well. Time is a remarkable gift. You can't work all the time, and you can't play all the time. Try to strike a balance that includes work, volunteering, leisure and sleep. You can't face life's challenges if you don't take time to recharge your batteries.

Be unapologetically yourself. There is only one you. Take time to think about what you truly believe in and what you want others to see. People will respect you for not compromising your principles, and they will know they can depend on you to be honest with them.

In business, the lessons you learn over time are your most valuable assets. They shape your decisions, guide your actions and ultimately determine your success. Embrace these lessons and let them steer you toward a prosperous future.

Mackay's Moral: The more candles on my birthday cake, the more I have to reflect on the icing of life's lessons.

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Harvey Mackay is the author of the New York Times bestseller "Swim With the Sharks Without Being Eaten Alive." He can be reached through his website, www.harveymackay.com, by emailing harvey@mackay.com or by writing him at MackayMitchell Envelope Co., 2100 Elm St. SE, Minneapolis, MN 55414.