The Old Trafford chief, who will be 71 on New Year's Eve, collaborated with academics at the prestigious Harvard Business School in Boston studying his management style.
"Players these days have lived more sheltered lives, so they are much more fragile now than 25 years ago," he said.
"I was very aggressive all those years ago. I am passionate and want to win all the time. But today I'm more mellow.
"And I can better handle those more fragile players now. There's all this hype about hairdryers and anger and so on.
"But there's another side to it, which is more in terms of how I have fostered relations with people and developed the team over the years."