"It is a very precarious industry," said Ferguson.
"Very few managers last more than three or four years with a club nowadays and the lifespan of a manager is getting shorter and shorter.
"I count myself fortunate to spend so long at one club.
"I have not had to go through that turmoil. It is horrible."
Ferguson acknowledges the demands placed on managers are greater than they have ever been.
"Crowd participation has become more volatile," he said.
"The other day I saw of photograph of a United game against Leeds. All these warriors like Stiles, Hunter, Charlton and Crerand were scrapping in the middle of the pitch. But when you look at the crowd there is not a bit of emotion. They are just watching the spectacle.
"You would not get that now. The fans would be screaming blue murder. It is a very emotional industry. That emotion can get to everyone. You lose three or four games and you are in trouble."