" That is because you don't yet know how to deal with time," said Wen. "But I will teach you to deal with time as you would deal with a coat, to be worn when necessary and discarded when not."
"Will I have to wash it?" said Clodpool.
Wen gave him a long, slow look.
"That was either a very complex piece of thinking on your part, Clodpool, or you were just trying to overextend a metaphor in a rather stupid way. Which, do you think, it was?"
Clodpool looked at his feet. Then he looked at the sky. Then he looked at Wen.
"I think I am stupid, master."
"Good," said Wen. "It is fortuitous that you are my apprentice at this time, because if I can teach you, Clodpool, I can teach anyone. "

― Terry Pratchett , Thief of Time (Discworld, #26; Death, #5)