From the New York Times, Glenn Kramon's essay "Why You Should Send Thank-You Notes, Even Years Later" begins:

Your assignment today: Write a note of gratitude to someone to whom your thanks are overdue. It might be a schoolteacher, a relative, a former colleague or boss or someone who did you a huge favor.

Frustrated by the vitriol in so much of what we read and hear, I began asking my business students at Stanford for an antidote: Surprise someone with a long overdue email saying thank you. And make it cinematic. Make the recipient laugh and cry.

We’ve all read of the psychic benefits of generosity. Yet not enough people reap them through thank-you notes. Many of my students have been stunned by the reaction to such emails. Teachers and parents, consider asking your charges to send them; they’ll find that you really can make someone’s day.

... followed by some beautiful examples!

In Toki Pona, perhaps something like:

o pana e lipu tawa jan
o toki e ni la: pona tawa sina a

toki pona	rough translation
o pana e lipu tawa jan	send a letter to someone
o toki e ni la: pona tawa sina a	say this: thank you!

_{(here's a free Gift Link; cf Thank You, Mr Rogers (2018-10-02), Mantra - Give More Praise (2019-07-28), The Honor Was Mine (2020-08-25), toki sona - o pana e pona tawa sina pi tenpo kama (2024-08-28), Mantra - Ho'oponopono (2025-04-09), ...) - ^z - 2025-08-25}