Rooney always plays a five-a-side at the Carrington training ground with the same vigour as a Champions League final.
But the Manchester United star fears that attitude to his job is actually wearing him out.
And with a Treble to be won for United this season, plus the World Cup coming up in the summer, that is something he cannot afford.
Rooney said: "I am enjoying my football, playing well and managing myself better. That's paying off.
"I am not doing every training session where, normally, I would train as hard as I can.
"It's not due to my knee. But I have played a lot of games this year and it is about reining myself in in training.
"I am getting a bit older and wiser now and it is probably the best thing to do."
United boss Alex Ferguson voiced his concern last weekend that Rooney was doing too much.
The striker had played an hour of the Carling Cup final, despite having a knee problem, and then insisted on playing almost a full game for England against Egypt at Wembley three days later.
It led to Ferguson resting him last weekend for the game against Wolves, so he could be right for AC Milan on Wednesday But Rooney added: "I am proud to play for my country and I want to play for it unless I really can't."
His hot streak continued as he scored twice in a 4-0 thumping of the Italians.
That made it four in the tie for him, after he hit two in the San Siro in the 3-2 first leg win.
It was a result that puts United into the Champions League quarter-finals and gives them the confidence and belief that they can go on and win the trophy again.
Rooney declared: "I think this result is going to send a great message out about us. It was a great performance from us again.
"Against a team like Milan, to win so convincingly is a great result.
"A win like this gives you so much confidence - especially the game in Milan, where we went behind but came back to win 3-2.
"We have been in good form anyway over the last couple of months, yet this result and the one in Milan have given us that extra belief we can win the tournament this year.
"We are building up a nice head of steam and looking forward to the draw next week."
One team who will not be in the hat is Real Madrid, after they went out to Lyon at the same time United were stuffing Milan.
It means there is no dream final for Cristiano Ronaldo at Madrid's Bernabeu home.
Rooney said: "Real Madrid have gone out, which has got rid of one hurdle.
"You know if you got to the final and faced them in their own stadium, it would always be difficult."
Rooney now has 30 goals for the season, with his manager believing he can match Ronaldo's 42 of two seasons ago.
On-song Roo insisted: "Hopefully, I can win trophies and, if I get 42 goals as well, I will be delighted.
"This is my best season yet. I am scoring a lot and I am enjoying my football."
While Rooney has emerged as the latest hero and talisman for the club, a former hero bowed out of Old Trafford on Wednesday night.
David Beckham appeared as a second-half substitute for Milan with the game already up and got a tremendous ovation, seven years after leaving United for Real Madrid.
Rooney said: "David has been a great servant to this club and all the United players were delighted he got a great reception.
"I hope I can become as well respected and thought of here as David Beckham.
"I have plenty of years ahead of me and, if I get half of the plaudits that he has been getting, then I will be delighted."
Wayne Rooney says Manchester United will become even more prolific now their first choice central defensive partnership is back in action.
Thanks to Rooney's efforts, United have so far been able to make light of lengthy absences for Rio Ferdinand and Nemanja Vidic this season.
Already the duo's recovery from back and nerve problems respectively has had an impact, with United keeping successive clean sheets for the first time since October.
And, ahead of Saturday's Premier League encounter with Fulham, Rooney revealed the additional security means United can attack with greater conviction.
"It is always difficult when your defenders are injured," he told MUTV. "You base your team around a solid back four and we have not had that all season.
"We have used different defenders in different games but thankfully now Rio and Nemanja are back.
"It gives us more stability in defence and that should mean more opportunities to score."
Rooney took his tally to 30 for the season with his midweek brace against AC Milan, so it is little wonder Sir Alex Ferguson reacted with irritation on Friday when asked what he would do if the England striker got injured.
"I am not even thinking about that," Ferguson said. "Please, give me a break. Do you want to stick pins in us?"
Tempting fate or not, United tackle Fulham at Old Trafford knowing Rooney is pivotal to their hopes of glory.
A place in the last eight of the Champions League is already assured but it is a record 19th title - and an unprecedented fourth in a row - that is really driving Ferguson on.
"The record we are chasing is four titles in a row," he said. "That would be fantastic. It would be the 19th title. It would be the most in the league.
"It doesn't matter who you beat for that record, it's a record and we have got a chance."
Victory at Wolves last weekend may have been scrappy, but it contained exactly the right ingredients Ferguson looks for at this stage of the season.
He has been down this road so many times before and can sense glory again.
"That match was the best indicator of our chances," he said. "We have had these kind of games over the years, where players are prepared to battle against a very determined team.
"It is not the kind of game you like to watch or enjoy because it was such a battle.
"But the players stood up to it and wanted to win because of the importance of the game.
"That is the way it is going to be to the end of the season."