Or you ended up like this:

An Ethiopian Airlines Boeing 737-800, registration ET-AOB performing flight ET-343 from Khartoum (Sudan) to Addis Ababa (Ethiopia), was enroute at FL370 when the pilots fell asleep. The aircraft continued past the top of descent maintaining FL370 and continued along the FMC route set up for an approach to runway 25L without descending however. ATC tried to contact the crew numerous times without success. After overflying runway 25L at FL370 the autopilot disconnected, the disconnect wailer woke the crew up who then maneouvered the aircraft for a safe landing on runway 25L about 25 minutes after overflying the runway at FL370.

The aircraft remained on the ground for about 2.5 hours before departing for its next flight.

ADS-B data confirm the information, The Aviation Herald received, showing the aircraft maintained FL370 until after overflying the runway before the aircraft began to descend and maneouver for another approach.

http://avherald.com/h?article=4fd127fe&opt=2049

I still remember when this incident occurred. It may have been similar, or it may have just been a distraction. I've always been a fan of power napping, but obviously it should be clear who's turn it is, like "my controls", "your controls", "my nap" etc. I think Apollo astronauts could manage it.