1. When you think you've not paid your credit card and got charged, then check your statement and find out you had nothing owing that month anyhow.
2. When designing, you get the little spinning wheel after hours of hard work and it crashes. You reopen your file though and find you saved 5 minutes ago without realising. (An even better version of this and SUPER rare is when you are about to Force quit the application, and it suddenly comes back to life) NB: this one is also true of videogame saves.
3. Realising that you have leftovers in the fridge on a Monday night after a hectic day at work meaning no supermarket trip for muggins.