Today (and every day) I'm thankful for that time Mr. Friedlander told me not to be sorry.
I was applying to summer programs while I was in high school, and I needed two recommendation letters, so I asked my 10th grade Quantitative Chemistry and Physics (QCP) teacher, Mr. Friedlander, to write one. About a week later, I figured I should follow up, to make sure I didn't miss the deadline, and I said, "I'm sorry to bother you, but I wanted to check in on the letter of recommendation I asked you to write for me." And, after assuring me he would have it ready by the deadline, he said to me, firmly, "Don't be sorry. You're not bothering me."
That was the first time I recall anyone saying that to me, and it has since become a central tenet of mine. Perhaps you've heard me say to you, "Don't be sorry", or, "There's no need to be sorry", or, "Never apologize for doing your job." And just the other day, someone to whom I had previously said something to that effect, said back to me, "Never apologize!", so Mr. Friedlander's advice is now in at least its third generation, and I am thankful.