When I’m sitting with a client team that has just finished reporting a poor quarter, I often think of a lesson I learned from my high school friend Larry.

He was the natural musician in my class. I’m guessing you knew one, too. He showed up in junior high already playing Rolling Stones songs note-for-note. By the time we were in high school, he was playing like a pro. When we graduated and went off to our various pursuits, Larry headed to the prestigious Berklee College of Music in Boston.

A few years later, when we are all back, he kindly invited me to grab my guitar and play a set with his band at an airport lounge. It was one of the first times I played in front of people, and even though the patrons were far more interested in their drinks than in anything I was doing, I was a little nervous.

When we were done, Larry asked me how I felt. “Awful,” I said, and he asked me why. “I made a bunch of mistakes, and every time I made one, I couldn’t stop thinking about it. So I just made more mistakes.”

What Larry told me then has stayed with me for the last 40 years and is one of life’s great lessons:

“Of course, you made mistakes,” he said. “We all do. But here’s the thing. The instant you play a wrong note, that note is gone. You can’t get it back. So, you keep playing. When you’re done, you go back and think about the mistakes you made and figure out what you need to practice so you don’t make those particular mistakes again. That’s all you can do, and it’s how you get better.”

Back to my client teams. Sometimes when a team has missed its numbers or completed a low percentage of their Rocks (quarterly goals), they’ll try to skate right past it. It’s my job to make sure that doesn’t happen. We’re there to learn how to hold ourselves and each other accountable.

But sometimes they go the other way. Instead of ignoring their poor performance, they dive deep into self-recrimination, and try to use this to show how tough they are. This is almost as bad because while it may be cathartic, it doesn’t do anything to make the future better.

This is where Larry’s lesson comes in. That poor quarter we just reported? It’s gone. It’s in the past. Water under the bridge. We can’t get it back. No matter how much we obsess about it, there aren’t any do-overs.

There is only one productive thing we can use it for, and this is a must-do. We need to take a very clear-eyed, unemotional look at it and figure out what we need to work on, so we perform just a little better next time. Perhaps we need to a better job of holding ourselves accountable for hitting our weekly numbers. Maybe we set a few too many Rocks or were late to get started on them.

Whatever it is, teams that consistently learn and apply these incremental lessons gather momentum. The speed and quality of their playing improves quarter after quarter. They still make mistakes. But instead of feeling guilty about it, they just use those mistakes as opportunities to get better.

Try this. Before you know it, you’ll find that you’re playing like a rock star.