Lee Westwood said not doing "enough right" on the last day of the Open cost him the chance to win a first major.
The 40-year-old led by two shots after 54 holes but his worst round of the championship, a 75, saw him finish in a tie for third at Muirfield, four shots behind winner Phil Mickelson.
"I didn't play badly, but I didn't play great," said the Englishman.
"It's a tough course - you've got to have your 'A' game. I missed a few shots out there."
Westwood made five bogeys as he slid down the leaderboard to finish on one over, while American Mickelson shot the round of the day - a 66 - for a three-under total.
"Sometimes you play well and somebody plays a bit better and sometimes you play poorly," he added.
"I didn't really do either and Phil obviously played well. He shot the round of the day, five under par and birdied four out of [the last] six - that's a pretty special finish in a major championship.
"But you've got to play well to give yourself your own momentum, and I just couldn't get there today.
"I didn't do a lot wrong, I just didn't do enough right. I know what I've got to work on."
Westwood, who has finished either second or third at a major eight times in his 62 attempts, "really enjoyed" the experience of beginning the final round as leader.
He said: "It's where any professional golfer wants to be. It means a lot and you go out there and try your best, but there was no pressure.
"I was amazed to be in the lead going into the fourth round, because every time I turned into the wind I was really struggling.
"I didn't feel like I was striking the ball well but I putted lovely this weekend. I made my fair share so there was a lot of positives to take out of the week.
"I'm not too disappointed. I don't really get disappointed with golf any more."