Like when you're tilting back in your chair (in a high school class or something of the sort), and the chair suddenly starts to go. If you're lucky, you catch yourself before it goes backward. If you're not lucky, you land on the floor with a massive amount of noise.
Sometimes it happens metaphorically, like when you go in to work and before you even have a chance to settle in for the day you lose your job. (Which - although it has happened in the past, did not happen in the past week.) (I figured I should say that so my parents don't worry.) (Everyone say "hi" to my mom and dad!)
Sometimes, however, it happens literally. Like when you're sitting at the house of some friends and watching the Olympic Opening Ceremonies, and you lean forward to scratch one of the dogs, and the chair just... well... kind of lurches forward. And you find that the front left leg of the chair has kind of come loose from its mooring.
Thankfully, they're good friends with a sense of humor, and they immediately said that the chair was a thrift-store find, not a big deal, and headed for the "to be fixed" area of the basement.
Oh. And I spent much of the rest of the night sitting on the floor and scratching the dog. It just seemed safer.
(And, well... I feel a tad guilty about it, even so.)