A strong young man at a construction site was bragging that he could out-do anyone in a feat of strength.
He made a special case of making fun of one of the older workmen. After several minutes, the older worker had enough.
'Why don't you put your money where your mouth is,' he said. 'I'll bet a week's wages that I can haul something in a wheelbarrow over to that building, that you won't be able to wheel back.'
'You're on, old man,' the braggart replied. 'Let's see you do it.' The old man reached out and grabbed the wheelbarrow by the handles.
Then, nodding to the young man, he said, 'All right, Dumb Ass, get in.'
Never mess with old people.