Each birthday, I find myself thinking about life and meaning. What have I done with my life? Where have I been? Where am I going? You know, the big questions. And this time around, I find myself reflecting particularly on regret. Specifically, on one sobering realization: mistakes are often permanent. There are no do-overs.

There was a time in my life when I didn’t have regrets. In a job interview back when I was a (very) young adult, my interviewer asked me if I had any regrets. It took me by surprise. I had never been asked that before, and I had never really thought about it before. I tried to do right, be good to people, be dependable. I didn’t feel like I had much to regret. I answered, quite sincerely, that I had no regrets. But then, during that interview, it struck me: I regretted dropping out of college. I just never fully realized it until the moment that I was encouraged, in a job interview of all places, to think about it. And it bothered me. It turns out it bothered me a lot: I got the job, but in less than a year I had re-enrolled at my old university to finish what I had started. And since it was 200 miles away, I quit my job and moved out of town as well.

And I got my college degree. Thankfully, some mistakes can be undone.

Unfortunately, many mistakes—far too many mistakes, in my experience—are permanent. Many things you say or do (and even things you might not say or do) don’t have a rewind button. They can’t be taken back, they can’t be undone. Some of these irreversible missteps can cause so much harm to your relationships or your reputation that they can never be repaired, not fully.

And I find that my regrets are compounded with age! As I grow in wisdom, I become aware of things I have done and said that I didn’t even recognize at the time were so regrettable, and am now all too aware of how harmful they were to myself—or worse, to the ones I love.

But there’s a lesson in these painful realizations, and I believe it is this: live your life like it matters. Strive to do your best, always. With rare exceptions, there are no do-overs…so act like it.