Rory McIlroy believes last week's controversial withdrawal from the Honda Classic could prove a blessing in disguise as he looks to play golf with a smile on his face once more.

McIlroy quit midway through his second round at PGA National, where he was the defending champion, initially telling reporters he was in "a bad place mentally" and then issuing a statement citing severe toothache as the reason for withdrawing.

The Manchester United fan admits that was still "no excuse" for quitting, referencing his side's controversial Champions League exit to Real Madrid by joking: "I gave myself a red card last week!"

He says he lost control of rational thinking after a flurry of dropped shots and concedes his tooth problem was a flimsy reason for pulling out.

But he has promised to learn from his mistakes and to try not to put so much pressure on himself to perform well.

"I had a lot of time to think about it and realised pretty quickly it wasn't the right thing to do," McIlroy said at a pre-tournament press conference ahead of this week's WGC-Cadillac Championship in Miami.

"No matter how bad I was playing I should have stayed out there. At that point in time I was all over the place and saw red. It was a mistake, everyone makes mistakes. I am learning from them.

"Some people have the pleasure I guess of making mistakes in private, most of my mistakes are in the public eye. I regret what I did but it's over now and it won't happen again.

"I actually think in the long run Friday will be a blessing in disguise. It was like it just relieved a valve and all that pressure I was putting on myself just went away. It's not life or death out there, it's only a game and I had sort of forgotten that this year."

Asked which reason for withdrawing was true, McIlroy added: "Both. I wasn't in a good place. Mentally my head was all over the place but at the same time I have been struggling with my lower right wisdom tooth for over a year.

"I had braces on for six months last year to try to relieve some of the pressure on it, I am taking medication until I get home to Northern Ireland and see my dentist, who would be the only guy I trust to take it out. My tooth was bothering me, but it wasn't bothering me enough to quit.

"When the going gets tough I have to stick in there a bit more and grind it out. There is no excuse for quitting and it doesn't set a good example for the kids watching. I feel like I let a lot of people down and for that I am very sorry."

With five wins last year, one of them being his second major title, not to mention playing his part in an amazing Ryder Cup victory, it would seem McIlroy has nothing to prove.

But that is not the case according to the 23-year-old Northern Irishman, who signed a multi-million pound deal with Nike earlier this year, but has since missed the cut in Abu Dhabi and lost in the first round of the Accenture Match Play Championship to Shane Lowry.

"I have been putting a lot of pressure on myself to perform and I have been working so hard and not really getting much out of it," he added.

"That's been the frustrating thing. It was the build-up of high expectations from myself coming off the back of such a great year last year and wanting to continue that this year and not being able to do it. I just let it all get to me.

"I've got to remember I started to play golf because I love it, I have to go out there and enjoy myself. Dave Stockton (his putting coach) said to me, 'When I see you out there you're not smiling, smile more'.

"When I smile it lifts your spirits and that was the whole turn around from last summer as well. When you start to enjoy yourself you start to play better and I haven't been enjoying it because I have been putting so much pressure on myself.

"I am going to go out there and enjoy it. I have four rounds thankfully (there is no halfway cut at Doral) and I'm going to go out and have a good time."