Emma Raducanu withdrew from Wimbledon on the advice of medical staff after she "started to breathe heavily and felt dizzy".
In a statement, the 18-year-old said: "Hi guys, I wanted to let everyone know that I'm feeling much better this morning. First up I want to congratulate Ajla on an incredible performance and I'm sorry our match ended the way it did.
"I was playing the best tennis of my life in front of an amazing crowd this week and I think the whole experience caught up with me. At the end of the first set, after some super intense rallies, I started to breathe heavily and felt dizzy.
"The medical team advised me not to continue and, although it felt like the hardest thing in the world not to be able to finish my Wimbledon on the court, I was not well enough to carry on.
"I want to thank the people who have cheered me on every single match, I wanted to win so badly for you! I also want to thank the All England Club, my team, the LTA, my parents and friends.
"Last night will go a long way to helping me learn what it takes to perform at the top. I will cherish everything we have achieved together this week and come back stronger! Can't wait to see what's next on my journey."
In an interview with the BBC, she added the exact cause of the incident was unknown but she thought it was a "combination of everything that has gone on behind the scenes in the last week and accumulation of the excitement and the buzz".
And the 18-year-old said before the tournament the largest crowd she had played in front of was about 100 people.
Footballer Marcus Rashford told Raducanu a similar thing had happened to him while playing for England Under-16s against Wales.
He tweeted: "I remember it to this day. No explanation for it and it never happened again.
"You should be very proud of yourself. The country is proud of you. Glad to read your feeling better."
Raducanu's withdrawal came in the second set of her last 16 tie against Australian Ajla Tomljanovic on Court One on Monday.
Already a set down, Raducanu was 3-0 behind in the second to the world number 75 when she received medical attention courtside from the trainer and doctor.
She had been noticeably struggling to breathe and, after consulting with them, she walked off Court One for a medical timeout.
Shortly afterwards, the chair umpire announced Raducanu could not continue with her fourth round clash to groans of disappointment from the crowd.
Raducanu, who is ranked 338th in the world, on Saturday became the youngest British woman to make it through to the second week at SW19 in the open era with a 6-3 7-5 win over world number 45 Sorana Cirstea in round three.
Public figures, including Piers Morgan, have been criticised for their opinions on Raducanu's withdrawal, with Andy Murray among those who defended the young star.
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