"It is impossible for a man to learn what he thinks he already knows."
Epictetus via the Daily Stoic
I've made this mistake as much as the next person, and I've probably missed out on plenty of learning opportunities because I've tuned people out thinking, "I already know this stuff."
While I may have had a firm grasp on the subject matter I thought I already knew, there is no doubt in my mind that I have missed out on some nuanced tidbit of information that I could have used to further the knowledge I already possessed.
In doing this, you not only cheat yourself, but you also cheat your players, your teammates, your students, your colleagues, your bosses, your employees, your significant others, your children, your friends...basically anyone you encounter. You cheat them by not becoming a better version of you.
And that should be the goal every day.
Don't be a know it all.
You can't know it all.
All you can do is continue to seek a better understanding of it all.
Experts become experts because of an insatiable desire to know more. The day an expert stops learning is the day their expertise begins to deteriorate.
Everything is a learning experience.
Go into learning experiences a blank slate, as if you know nothing.
You might just learn something.