I love this piece in the Harvard Business Review. Such a simple but powerful concept.
Positive feedback can really make your day, a colleague recently gave me wonderful feedback on a piece of work I had done for them and I felt great all day. And the next. This takes it to the next level, I defy anyone not to blossom with praise and appreciation, and with a note you can go back on a gloomy day and remind yourself how others see you. I wonder if it will work with my children too.