This comes from the ancient Jewish practice of Mussar, the study of character-building. I first learned about Mussar from Tiffany Schlain (Webby Award founder) when I saw a film she created as part of a 2014 project she entitled Character Day.
The idea is very simple. From the film's transcript:
For example, say you want to increase your sense of gratitude, which there's so much research today saying that if you feel more grateful you're gonna be healthier you're gonna have more mental strength and you're gonna sleep better.
There's a practice on gratitude based on the Jewish tradition of a hundred blessings a day. My good friend Armas first taught me about it. Every day you say say a hundred blessings. Everything from waking up first thing in the morning to the big moments to the little moments. Even when you go to the bathroom (that's the Jewish way).
100 blessings every day. Do I say them? I try.
At the end of the day as you're going to sleep instead of looking at your screen close your eyes and think about all those moments all those things are grateful for.