I learned LCD, Least Common Denominator not ... whatever it is now.
Actually, I just retired as a truck driver and my job was to make a lot of money and get no sleep, have no life, don't kill you and don't get killed.
The hardest and most demanding part of my job was staying awake and maintaining health.
(Ever get the flu with 102 temp. 600 miles from home, no time nor means to go to a doctor/ER, living in a 3' x 6' bunk?)