Man goes for a physical

"You're in incredibly fine condition," the doctor concluded after finishing a thorough physical.
"How old did you say you were, sir?"
"Seventy-eight."
"Seventy-eight! Why, you have the health of a sixty-year old. What's your secret?"
"I guess, Doc, it's due to a pact the wife and i made when we got married. she promised that if she was ever about to lose her temper, she'd stay in the kitchen 'till she cooled off. And i pledged that when i got angry I'd keep quiet, too, and go outside until i calmed down."
"I don't understand," the doctor said. "How could that help you stay so fit?"
"Well," the patient explained, "I guess you could say I've lived an outdoor life."