I saw a thing on Pinterest that's basically the same thing. Every day you write down the good things that happen on a notecard and put it in a jar of something. Then when you really need it, you pull out a couple of random ones and put them in a second jar, so you pull out new ones each time... Then once the first jar is empty, you start from the second one... It works on a more regular basis because you're not remembering the same things over and over...