One of my college professors once said, “I used to be a doctor” during a lecture about business strategy. I instantly put up my hand to ask him why he switched careers. I wondered whether procrastination was involved.

He laughed and said:

“I went to med school and worked as a GP for nearly 20 years. Then, I thought, I actually want to become an academic so I got my Ph.D. in business. And now I’m in my second chapter.” 

I was intrigued and went to him after class. “May I ask how old you are?” I asked.

“I’m 61. And I got my Ph.D. when I was 55,” he replied. I was surprised and he could tell. I had never heard of someone who made such a big career switch at that age.

In my environment people gave up on learning and developing themselves in their 40s. So I asked, “How did you make that decision?” He answered:

“Life is long and you can do a lot of things. I let my curiosity drive me. For example, just the other week, I read about something fascinating. If you combine all the energy that the stars give off, it’s much more than the energy the sun gives. So why is it dark at night?”

“I have no clue,” I replied.

“You’re not alone. In fact, no one knows. It actually shouldn’t be dark at night. Isn’t that fascinating?”

I still use that example every time I talk about the mysteries of life and the limitations of human knowledge. There are many things we don’t know. I asked the professor about what it was like to go back to school in his 50s.

“I don’t regret it for a second. I knew it was something I wanted to do. I actually wanted to do it many years earlier. If I didn’t go for it, I knew I would regret it later in life.”