Knowing how to leave a party is an important life skill. This does not get enough attention. Plenty of angst and instruction and practice goes into mastering the entry: when to arrive; what opening line to use; what to bring. As for the exit, well, you’ll figure that out when the time comes—just feel the room. Everyone will probably be sloshed by then anyhow. That system tends not to work and, consequently, most parties stumble across the finish line like a marathoner who ran the opening mile at full speed. People stick around too long; they fall asleep; they pass out.…