I was often looking for nice things to do for my Mom. One day, I
noticed that she often had a hard time opening two-liter soda bottles.
I got an idea, and snuck out into the garage, where we kept a supply
of soda. Methodically, I went through each and every soda bottle and
unscrewed and unscrewed and re-tightened the caps (but not too
tight!). It was a big supply, and there must have been at least
twenty bottles out there.
I snuck back inside and waited. After a couple of days, Mom hadn't
said anything, so I asked her if she'd noticed anything about the soda
bottles -- that, say, they were a little easier to open? "Why? What
did you do?" asked Mom. I explained my good deed to her. She took it
rather well, seeing as the intention was good, but we did drink a lot
of soda very quickly over the next few days.