Irish amateur Paul Dunne insists it was his own game and not the high-pressure atmosphere of being in the final on the last day of the Open which spooked him.
The 22-year-old began the day as joint leader on 12 under, after a brilliant 66 in the third round, seeking to become the first amateur since Bobby Jones in 1930 to win the Open.
However, he never really gave himself a chance after duffing his approach to the first short of the burn and then sliced his tee shot at the next onto the tournament's practice chipping green.
He recovered those two dropped shots by the fifth but by then his rivals were pulling away and a back nine of 40 saw him finish on six under, nine shots off making the play-off alongside playing partner Louis Oosthuizen, Zach Johnson and Marc Leishman.
"I was nervous but nothing anything different to the last three days," he said.
"But the last three days I got off to a steady start and settled into the round and today I had a couple shots that I hadn't seen in any practice or any range sessions I've had.
"It kind of just rattled me a little bit. I didn't really know where they came from and I just never settled in after it.
"I don't think there are many positives to put on a 78 in a final round but I'm sure there's still stuff I can learn from it that'll be positive going forward and help me in the future."
Before this week Dunne was still planning on playing in the Walker Cup at Royal Lytham and St Annes in September but his performance at St Andrews may produce a change of heart.
"I haven't really been thinking about it," added the Irishman, who graduated from the University of Alabama with a degree in business finance in April.
"I've got to go tomorrow morning to a Walker Cup practice session at Lytham so I'll just think about it for the next few days and make a decision but right now there's nothing concrete
"I have 10 days off in my schedule anyway so I'll just get some rest.
"I've played a lot of golf since I've come back from America so I kind of need a bit of a break after that and a bit of recovery and reflection."