Great Britain's Adele Nicoll lamented her 18th-place finish in the Winter Olympics monobob, saying she was "speechless" and "in shock".
Nicoll's reaction was in contrast to Newport's "so happy" Mica Moore, who finished 14th competing for Jamaica at Milan-Cortina.
Welsh competitor Nicoll, 29, made history as the first woman to compete for Team GB in the event.
Her fourth and final heat time of 1:01.03 was the slowest of the round and gave her an overall time of 4:01.86.
"That last run is just not reflective of my capabilities as a pilot," said Nicoll.
"It was probably the worst run I've ever had in my life, which is not ideal in an Olympic Games."
USA's Elana Meyers Taylor won gold aged 41 and celebrated with her children as she capped a career which includes two bronzes and three silvers.
Nicoll, who aims to compete in the shot put for Wales at the 2026 Glasgow Commonwealth Games in the summer, finished one minute and twelve seconds behind Meyers Taylor.
"I put down three really solid runs and I think maybe what shows is that you need to put four solid runs down to keep your position," added Nicoll.
"I was 11th going into the final run and maybe a lack of experience has not done me too well.
"My best performance so far in a World Cup has been 12th so to be sat 11th going into that final run was a great achievement and unfortunately I just couldn't lay down that fourth run."
Nicoll, from Welshpool, will have to shake off the disappointment as she turns her attention to the two-woman bobsleigh event as pilot alongside former GB sprinter Ashleigh Nelson.
"I am extremely disappointed and I do feel like I've let everybody down but I am sure I will process it and I'll take that with me into the two-woman," she said.
"The monobob was never the strong event coming into the Games, the two-woman has always been our stronger event. I am really proud of myself for the three solid runs and to be sat 11th going into the last run shows the potential.
"I know everything that could have gone wrong did go wrong and it is just one of those nightmare performances that I'll hopefully move on from."
Nicoll - a three-time British shot put champion - was a travelling reserve for the two-woman bobsleigh at the 2022 Games in Beijing where the monobob made its debut as a Winter Olympics event.
"Hopefully that shows people that this is raw and it is not all sunshine and rainbows," Nicoll added.
"I've had to overcome a lot of hurdles to even be here. I started off this season not even walking and had to overcome a serious injury to even be on the starting block today.
"I am just taking some accountability for that fourth run not being good enough and I need to pull it together for the two-woman."
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'Really proud moment' for Moore
Jamaica's Mica Moore, from Newport in south Wales, finished four places ahead of Nicoll in 14th and was delighted with the outcome following her switch in 2022 from representing GB after claiming she had witnessed "damaging and offensive behaviour".
Moore told BBC Sport: "I'm so happy. It has been a real tough journey to get here, it hasn't been easy at all. I guess to me it is just a story of not giving up.
"I had a really difficult time with Great Britain and that is not secret at all and I'm just so proud I didn't give up on myself and I'm so grateful for my family and friends for digging myself out of the trenches when it was really tough and just keep going. Moments like this make it really worth it."
Moore began her sporting career as an athlete - representing Wales at the 2014 Commonwealth Games - before switching to bobsleigh.
Her grandfather, Venson Byfield, came to the UK in the Windrush generation and settled in Wales.
"It is a really proud moment," she added.
"I've spoken a lot about my grandfather and how we came over with the Windrush generation and I never got the pleasure of meeting him, but my mum has told me so many stories about him and I just had that in my heart the whole time. I just wanted to make my family proud.
"They've supported me for so long. I'm 33 now so I'm quite old and they've never wavered in their support.
"I've just had the most lovely career because of them."