O'Sullivan, who was scheduled to face John Higgins at Alexandra Palace in the first round, withdrew on medical grounds two days before the tournament began.
Speaking to Eurosport, the Rocket said: "If you'd have asked me Sunday was I ready to play, I probably would have been OK, but it's such a massive tournament.
"I've obviously been on this three-week trip away playing and I just think I exhausted myself. A lot of pressure while I was away, and I just think the build-up of all that kind of just got a bit too much, really."
The withdrawal came amidst a challenging season for O'Sullivan, who has struggled for form and suffered a series of surprise defeats throughout the year.
His recent performances have been inconsistent, including early exits at the UK Championship and the Riyadh Season Snooker Championship.
O'Sullivan's frustration boiled over during the Championship League last week in Leicester, where he snapped his cue in anger following a defeat to Robert Milkins.
This incident and his overall exhaustion ultimately led to his decision to withdraw from the Masters.
"I lost the plot on Thursday, snapped my cue, so that's unplayable," he admitted.
"I knew that at that moment in time, the right decision was to not play. And it’s such a big tournament, I thought whoever was going to come in should have at least had a couple of days' notice."
Despite the setback, O'Sullivan remains optimistic about his future in the sport. He expressed his desire to return to the Masters and compete for the title once again.
"This is an unbelievable tournament," he said. "Top 16 best players in the world, amazing crowd. You know, I’ve won this tournament many times, like 14 finals. I'd love to come here and play again and hopefully be lucky enough to win the trophy again. That'd be great."
O'Sullivan's withdrawal paved the way for Neil Robertson, who staged a remarkable comeback against Higgins in the first round to advance in the tournament.