David Morris, 27, became so ill that he was unable to care for himself and would spend most of his time hooked up to an oxygen tank.
But, shortly after being put on the waiting list to receive a double lung transplant, his life was dramatically turned around.
Morris' transplant success story comes after the Welsh government announced that, from 1 December, everyone in Wales will be automatically opted in to donate their organs after they die.
The 27-year-old told Wales Online: "I think the new legislation has got to be a good thing as it’s helping raise awareness of organ donation, and hopefully the outcome of this will mean more people as potential organ donors."
Morris was diagnosed with cystic fibrosis at birth, however his health deteriorated rapidly when he reached 18.
Cystic fibrosis is a genetic condition in which the lungs and digestive system become clogged with thick sticky mucus. According to the NHS there is no cure, however there are treatments available which aim to ease the symptoms and make the condition easier to live with.
In more severe cases, a lung transplant is required if the lungs become "extensively damaged".
Despite his best efforts to remain fit and healthy, the severity of Morris' illness meant that he ended up on oxygen for most of the day and it became increasingly impossible to take care of himself.
In February 2014, the avid cyclist from Brecon, Wales was put on the transplant list and waited just nine months before having a double lung transplant which, he says, has turned his life around.
Morris says that he backs the Welsh government's move to make organ donation an "opt out" process.
Currently, the scheme across the UK requires those who want to donate their organs after death to sign up to the NHS Organ Donor register.
However, under the new initiative, everyone living in Wales will be automatically opted in to donate their organs after death. And those who don't want to, will simply have to "opt out".
Ministers believe that this will improve transplant rates and will benefit the people of Wales by reducing the number of people dying whilst waiting for a suitable organ to become available and improving the lives of others.
An advertisement aired on TV hopes to raise awareness of organ donation and get people thinking about what choice they'll make come December.
"Life was tough [before the transplant]," revealed Morris. "But then I received the call that a suitable match had been found and I was to receive a double lung transplant. From then on, life changed pretty quickly – and has been brilliant ever since."
"I appreciate how lucky I’ve been. My life has been completely turned around as a result of getting a new pair of lungs and I’ll be eternally grateful to the donor and their family for giving me this second chance at life."