Here are some sequences of events:Take the rake out of the shed, use it to pile up the leaves in the backyard, then put the rake back in the shed.Fly to Seattle, see the sights, then fly home.Put the key in the door, open it, then take the key out of the door.Wake-up your phone, check the time, then put it back to sleep.See the pattern? You do something, then do something else, then you undo the first thing. Or more accurately, the last step is the inverse of the first. Once you're aware of this pattern, you'll see it everywhere. Pick up the cup, take a sip of coffee, put the cup down. And it'...