Rooney, the subject of two confirmed bids by the Blues in the recent transfer window, bagged his 200th United goal in a 4-2 Champions League win over Bayer Leverkusen on Tuesday.
The England star has impressed this season despite struggling with injuries and persistent rumours that he wants out of Old Trafford.
"I've put my head down and worked hard and tried to do everything right," Rooney told The Mirror.
"I've tried to show the right attitude. I've always felt that's a really important thing to do.
"That's paying off for me on the pitch. I feel fit and ready to do well.
"I feel good. I've had some good training the last few weeks. It's been stop-start with the injuries, but I've just kept my head down and worked hard and now I've played and got some goals.
"I feel great. The training is a bit different under the new manager - I remember it from Everton, it's more intense. That's helping me.
"I feel good and am glad to be out playing."
Rooney also backed manager David Moyes to impress in the Red Devils hotseat.
"He's a great manager and thoroughly deserves this job because of what he did at Everton. It's good to work under him and hopefully be successful together," Rooney added.