"For those who don't know, this is a famous story that has repeatedly been told around acting circles. The story is that when Dustin Hoffman was involved with the movie Marathon Man, his character was depicted as looking like he had stayed awake for three nights. Dustin, being a method actor, decided to stay up for three nights in real life in order for it to look more realistic. When he came to the set, Laurence Olivier (An actor some consider one of the greatest in the world) asked him why he looked so tired and Dustin told him. Then Olivier pauses for a moment, then makes the famous statement, 'Try acting, dear boy...it's much easier.' Thus, this legendary tale was born. Lots of articles have different version of the story." - from www.simplydustinhoffman.com
For those of you who know this story, it's worth another look because there is MORE to the legendary tale than we knew: LINK