You know how much I love letters. You know how much I value the art of the handwritten note in showing concern, care, and appreciation.

Yet sometimes a formal thank-you note seems... odd.

• Though I might write a note of appreciation as a surprise, I’ve never written a formal thank-you note to a boyfriend after he treated me to dinner or bought me a gift.

• Growing up, I never wrote my parents thank-you notes after Christmas or my birthday, though they had bought me gifts for both occasions and threw a party for the latter.

• In times I’ve lived with other people, I haven’t routinely written thank-you notes when they handled a household chore or took care of something around the home for me when I traveled for work. (If traveling for play, I’d always bring back a small appreciation gift—but never wrote a formal note to accompany it.)

• My brother regularly has groups of friends and family over to his house to watch a big game or a television show (he and I love “The Amazing Race”). I haven’t written him a proper thank-you note after any of these occasions.

Yet maybe I’ve made mistakes all these years—and thank-you notes have wider application than I’d thought.

When else might a thank-you note might seem tone-deaf?