As I sat next to her bed in the intensive care unit, I wondered if she knew that today was her last day when she woke up this morning. I didn’t think she knew that it was her last day now. I was sure that she knew that something was wrong but did she know that she’d be dead in a few hours?

One of the most profound things about being a physician is the perspective on life that the job gives me. People who I barely know invite me into the most intimate aspects of their lives. I’m involved in helping people through what are often the most challenging and life-changing moments of their lives. It’s an incredible privilege, a profound responsibility and an educational experience like none other. It has made me a more understanding and better person.

About a half dozen years ago, I was almost killed when a car made a left turn through a traffic signal and ran me over while I was riding my bike. I wound up laying in the gutter in a somewhat dissociated state listening to these very troubling involuntary moans coming out of my mouth, with incredible pain in my side and feeling myself getting cold as I was going into shock.

“I just want to see my son again. I don’t want to die on the side of the road.”

I did not. And during the month I spent in the hospital and the months I spent recovering, I realized two things. First, five seconds either way and that accident never would have happened. It was just fate. It was uncontrollable. Second, that event became a catalyst for change in my life. Like a lot of people, my life had become a routine that was in many ways unsatisfying. I was financially comfortable but emotionally and spiritually unhappy. I was settling. And life, as I’ve learned, is too short and unpredictable to just settle.

All of this went through my mind on that Father’s Day as I watched the woman in the ICU. Her day had been uneventful until she developed the horrible pain that signaled the start of her aortic dissection. She was elderly and frail, and there were really not many good options for her even under the best circumstances.

But soon her leaking aorta would open completely, her blood pressure would go to zero, and that would be the end. If she knew that would happen today, would her day have been different? Would she have called her son to say that she loved him and thank him for taking care of her? If she knew months ago or years ago that this would happen on this day, would she have changed anything?

She had no way of knowing. None of us do. And I spend every day in the office and hospital talking with people who are unhappy with their lives. They’re unhappy in relationships. They’re unhappy with their health. They’re unhappy with their jobs. They’re unhappy about all manner of things that often times are completely within their power to change. But they don’t. “Tomorrow,” they say. “When school gets out,” they say.

Today happens once. And we are guaranteed nothing. To fret over the past and put things off on the future only squanders today. Be kind to yourself. Be kind to others. Become the person that you always wanted to be. Look around and find the good things because they are out there. When I can do that, my days are full and rich and satisfying, and I feel like I help make the lives of people around me better, too. And in the end, that’s all that matters.

Michael P. Jones is a gastroenterologist.