Five-time world champion O'Sullivan won his sixth Masters in January and his fourth Welsh Open title in February.
"I know I won the Welsh Open and the masters but, the masters, I only won it because everyone played pretty abysmal against me," he told BBC Radio Wales.
"Winning two tournaments was a bit too much return for how I've been playing."
O'Sullivan lost 4-3 to world number 31 Michael Holt at Venue Cymru on Tuesday.
"Well done to Michael. He played a good match and deserved his win. He played better on the day," O'Sullivan continued.
"I wasn't really on form. I was pleased with how I stuck in there and tried to turn it around but my game just wasn't strong enough.
"I think I've overachieved for how I've been playing. All I've had really is one good week in Wales [at the Welsh Open].
"I've probably just been papering over the cracks really.
"For me to do well at [the World Championship in] Sheffield, I'm going to need to find some consistency.
"I need to do some work between now and when Sheffield starts."
Holt, who made breaks of 119 and 88 to establish an early advantage against O'Sullivan, faces either Liang Wenbo of China or Graeme Dott of Scotland in round two on Thursday.
"It's great to beat him [O'Sullivan]. He's the best player," Holt said. "It's up there with one of my best wins.
"For him to say good things about me - there is probably not a better compliment in the game. It's nice because he knows what a good player looks like."
Ronnie O'Sullivan is unhappy with his displays in 2016, after being knocked out in the first round of the World Grand Prix in Llandudno on Tuesday.