Rooney, who came face to face with the World Cup trophy in London yesterday, will carry the hopes of the nation when England head for South Africa this summer.
Golden chance: Rooney likes the look of the World Cup in London
The 24-year-old has been in such outstanding form for United it has raised fears among England fans that he cannot maintain the same standard right through to June.
But Rooney has revealed that he has cut down on the amount of training he does at United to ensure hestays fresh.
VIDEO: Rooney eyes World Cup.He said: 'I am enjoying my football and playing well and managing myself better and that's paying off. I am not doing every training session whereas normally I would train as hard as I can every session.
'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.'
Magical form: Rooney fires his 30th of the season past AC Milan keeper Christian Abbiati
Rooney stressed he will continue to play for England when he physically can. The striker was criticised by boss Sir Alex Ferguson at the weekend for playing in a friendly against Egypt last week despite carrying a knee injury.
Rooney missed the subsequent United game at Wolves but returned to action with two goals in Wednesday night's 4-0 defeat of AC Milan at Old Trafford.
Head start: Rooney is keeping himself fresh for South Africa
He said: 'I am proud to play for my country and I want to play for them unless I really can't.'
Rooney has 30 goals in all competitions this season, raising hopes he can surpass Cristiano Ronaldo's 42-goal haul of two years ago.
MARTIN SAMUEL: How Ronaldo's exit turned Rooney into the real dealMANCHESTER UNITED FC