In a wide-ranging interview with L'Equipe, covering happiness, spirituality and psychology, the 21-year-old American – who rode for Continental team Axeon Hagens Berman during the 2016 and 2017 seasons, described how he has been able to retain his love of life outdoors. When it comes to his future, he said, "I just know that I'd like to do something that could help others."
Costa had already decided to stop cycling competitively the year before his accident, with his last races having been at a series of under-23 events in Italy in April 2017. In a Axeon Hagens Berman team statement released ahead of the 2018 season, Costa said: "I'm just not ready to come back yet. The more I thought about it, the more I realised I didn’t want to hold a spot on the team when that meant denying someone else of the opportunity.
"Since I stopped racing in April 2017, I've learned a lot about myself and realised how big, and unbalanced, of a part of me was cycling. I knew that if I was going to race again, it'd be in a much different, more relaxed way. I wasn't able anymore to have the single-minded, razor-sharp focus for training and racing that I once woke up with daily. I knew I had to lean on other things in life to provide me more balance and more happiness overall."
Costa's other interests included climbing, and it was while on Mount Conness, California, in July 2018, that he fell, trapping his right leg under a rock.
After calling out for help, Costa was found by another group of climbers, although it was another six hours until a rescue team could get to him.
"I have a big responsibility to make the most of this second chance"
Once at the hospital, Costa's right leg was amputated below the knee, and his life would change forever.
The biggest change, Costa told L'Equipe, is that he now feels "more responsible".
"I realise that I have a big responsibility to make the most of this second chance," he said. "I feel more connected, and connected to the world around me, natural and human, and that inspires me to give back something beautiful and lasting to this world.
"When I was stuck between the rocks, I realised that it was the tranquility that was going to save me – that I had to give in to the situation because, for the first time in my life, I found myself completely helpless.
"In English, we call it letting go," he told the French sports newspaper. "It allowed me to get out of my body and endure the hours of suffering, uncertainty and waiting. Afterwards, at the hospital, it was this incredible chain of people helping me that allowed me to see the beauty of life and allowed me to keep hoping, in particular."
After only a short time, Costa returned to physical activity, including riding again.
"Not even a month after the accident, I went to the gym, cycling with one leg, doing rehabilitation exercises and strengthening the amputated leg and my abs," he explained.
"I also went indoor climbing before having my prosthesis fitted, so I worked a lot on my arms. It was a real pleasure to be climbing again."
"I'd like to do something that could help others"
The climbing has remained a constant for Costa, who these days is studying at university, trying to find out a little more – like most people his age – about what he'd like to do next.
"I'm currently busy with my psychology studies at the University of Bend, in Oregon. I spend a lot of time 'training': lifting weights, indoor and outdoor climbing, skiing – and cycling, of course. It feels good to be here, near the mountains, in a quiet setting.
"I am interested more and more in psychology," said Costa. "I started doing meditation when I was still riding, and the idea of being able to push the physical limits on the bike with mind control fascinated me. And it was the meditation that actually made me realise that cycling [competitively] wasn't for me anymore. I wanted to find something deeper, more profound.
"So now I focus my studies on these cognitive and spiritual elements, and I read a lot about that," he continued, "and would like to do further study into that.
"Professionally, though, I still don't know what I'd like to focus on. Psychology is such a vast field. I just know that I'd like to do something that could help others.
"For now, I still consider myself an athlete," Costa told L'Equipe, "but I don't think I'll return to competition in a formal way. What inspires me is setting personal goals – to push my physical and mental limits."
"That's why mountaineering attracts me. Not only is it a discipline that combines elements of climbing, ice climbing, hiking and skiing, but it's also a mental challenge: about making the right decisions, knowing when to turn around, knowing when you have to push."