World number one Naomi Osaka said she had been suffering from headaches because of the stress of being top seed at a grand slam for the first time and admitted her shock exit from Roland Garros on Saturday was "the best thing" that could have happened.
The world No 1 from Japan saw her hopes of winning a third successive major ended by world number 42 Katerina Siniakova of the Czech Republic who pulled off a sensational 6-4, 6-2 victory.
"Losing is probably the best thing that could have happened," said 21-year-old Osaka, the reigning Australian and US Open champion.
"I felt very tired. In the other matches I had headaches, maybe that's the stress. I felt there was a weight on me. This hasn't been the happiest of times. On a disappointment level of 1-10 - I am probably at a 100 at the moment."
Osaka admitted that she had been "over-thinking" her game and her ambitions.
"I was over-thinking this calendar Grand Slam thing. It's something I wanted to do forever but if it was that easy, everybody would have done it."
She added: "I have to work hard now to put myself in the position to do it again. I'm peacing out of this tournament."
Osaka was undone by a shocking 38 unforced errors as she finally ran out of luck in Paris having had to come back from a set down in her first two matches.
"It's amazing, I can't believe it, I am so happy now," said Siniakova, who was the women's doubles champion in Paris in 2018 alongside Barbora Krejcikova.
"I played my best tennis and I hope it continues."
Osaka dropped the first set for the third successive match at the tournament, squandering seven break points in all.
Siniakova made her pay, breaking for 5-4 and taking the opener when Osaka sent back her 16th unforced error of the set.
The Czech, who is the world's number one doubles player, kept up the pressure on the misfiring top seed, breaking for a 3-2 lead in the second set.
Siniakova backed it up with another break for 5-2 off Osaka's third double fault of the match.
Victory was hers on Court Suzanne Lenglen when Osaka unleashed another misguided forehand.
The Czech goes on to face Madison Keys of the United States in what will be her first appearance in the last 16 of the majors.
Despite being top seed for the first time at a Slam, Osaka had never looked convincing in Paris.
She was two points away from defeat in the first round against Anna Karolina Schmiedlova and came back from a set and break down to see off Victoria Azarenka in round two.
Her defeat also means that only four of the top 10 seeds in the women's singles are left in the tournament.
"I don't want to say I was depressed -- that's too strong a statement," added Osaka.
"I have felt that before but this is not that extreme. I can say I am very disappointed but I can't turn back time."