The Jewish day of atonement. Unless medically contraindicated, you are to fast* fast, and to meditate on where you have failed to measure up this year†, and how you might be better next year.
The fast went quite well for me. My feet bothered me more than my stomach.
Just before the fast, we ate a meal of home made chicken pot pie‡ which was rather nice.
Natalie, our 10 year old daughter actually fasted until about 2:30 in the afternoon, which was quite impressive.
We got together with some neighbors for a break the fast which was a lot of fun too/
*This means no food OR water for about 25½ hours. Judaism is not a religion for wimps.
†Were I to post the list here, it would overload your browser.
‡You do not want to start a day without water with something spicy.