The 32-year-old's victory at Merion last month was the first by an Englishman since Tony Jacklin in 1970 but after playing the week afterwards he took a fortnight off.
It meant he arrived at Muirfield under-prepared for the 142nd Open Championship and he bowed out at 10-over.
"I had high hopes but I didn't really have the expectations," he said.
"Preparation has been unusual this week coming in here after two weeks off.
"The decision was made hoping I'd be playing well and I'd be mentally recharged for the weekend but this golf course proved too much for me this week.
"I wasn't quite prepared to play the US Open again. It played more like Shinnecock Hills in 2004 (where the fast greens were regarded unplayable despite watering as the play was taking place) than the Open Championship.
"I didn't have my game and you needed to be right on top of things playing this type of golf course.
"I felt three weeks was enough time to get ready and to be honest my game didn't feel great coming in here but I felt if I hung around I could get better each day.
"But with the conditions being really tough it didn't help that happen.
"This was brutally tough. I just wasn't quite up to the task.
"Majors are incredibly difficult to win and guys spend their whole careers trying to win one let alone more than one.
"A lot of things need to line up and you have to play your best stuff any time you play in the majors to have a chance."
Becoming a major champion places a lot of extra demands on players and Rose felt he needed to take the time off to enjoy something of a normal life.
So with that in mind he is not going to get too downhearted about his performance.
"I am three weeks removed from winning a major and it was just a bad week," he added.
"There are so many variables on that golf course I am not going to give myself a hard time about it.
"Maybe I wasn't 100% prepared for it but I'm not looking too deeply into it.
"I spent two weeks with my kids and had a life and enjoyed it. I have no regrets."