Well, Malcolm Myatt can. After having a stroke back in January 2004 while he was making breakfast, he has been in a permanent state of happiness.
The stroke affected his right frontal lobe in his brain and he spent nearly five months in hospital.
When he returned to his home in Cannock, Staffordshire, 68-year-old Malcolm was unable to walk long distances without the help of a stick and he had lost all use of his left arm.
But his family noticed another change in him.
His wife, Kath, 63, said: "Malcolm doesn't cry, he just doesn't know how to be sad anymore. But he's infectious. When he starts laughing everyone in the room does.
"We have been to funerals and I've been on tenterhooks wondering what he might come out with."
Luckily, Malcolm can look on the bright side of his condition and said: "I've always been a happy person and loved telling jokes but now I don't ever feel sad.
"I remember that I used to be able to feel sad, if something bad happened - but it just doesn't happen anymore. I would definitely rather be happy all the time than the other way around."