Every summer, I paint a rock. Just one rock. I've been doing this for years, ever since my daughter came for a visit and she brought a bag of rocks to paint. She had taken a class, or learned the technique from someone. I don't remember. She was good at painting animals and such, but I stuck to adding random colors without any plan. It is very relaxing, for some odd reason.
I just added this summer's rock. I keep them in a shallow pot on the patio. This time of year, it is a little cooler in the evenings, so sitting on the patio is tolerable. Every once in a while, I go through the pot, pull out a rock, and remember the events of the year I painted it. It is an odd ritual, but I enjoy it. And, as an added bonus, the pot of colorful rocks serves as yard art!