The world number one was heavily criticized after he quit the tournament midway through Friday's second round with what was initially a mysterious explanation.
The Northern Irishman was playing badly and appeared certain to miss the cut when he shook hands with his playing partners after just eight holes. Before leaving the course, McIlroy told reporters he was in a "bad place mentally."
Shortly after he issued a statement blaming his early exit on a severe toothache while apologising for quitting, but now admits he should have kept playing.
"It was a reactive decision," he told Sports Illustrated about quitting after he hit his approach shot into the water on the par-five 18th, his ninth hole of the day.
"What I should have done is take my drop, chip it on, try to make a five and play my hardest on the back nine, even if I shot 85.
"What I did was not good for the tournament, not good for the kids and the fans who were out there watching me - it was not the right thing to do."
McIlroy has been struggling all year after switching clubs but reaffirmed his belief that his equipment was not to blame.
The 23-year-old said he needed to adopt a tougher approach and would do well to copy Tiger Woods, the man he is most often compared to.
"He might be the best athlete ever, in terms of his ability to grind it out," McIlroy said. "I could have a bit more of that, if I'm honest."
