Former Wales captain Ryan Jones, who played 75 tests for his country, has revealed his fears for the future after being diagnosed with early-onset dementia aged 41.
Jones, who retired from rugby in 2015, received the diagnosis of probable chronic traumatic encephalopathy (CTE) in December last year.
In an interview with the Sunday Times, the lock and backrower said: "I feel like my world is falling apart.
"I am really scared because I've got three children and three step-children and I want to be a fantastic dad.
"I lived 15 years of my life like a superhero and I'm not. I don't know what the future holds.
"I am a product of an environment that is all about process and human performance. I'm not able to perform like I could, and I just want to lead a happy, healthy, normal life.
"I feel that's been taken away and there's nothing I can do.
"I can't train harder, I can't play the referee, I don't know what the rules of the game are anymore."
After being diagnosed with depression Jones, who toured New Zealand with the British and Irish Lions in 2005, said he began to have short-term memory problems and was becoming forgetful.
"It terrifies me because I don't know if, in two years' time, we're sat here and these episodes are a week long, two weeks long or permanent," said Jones.
"That's the fear, that's the bit that never leaves. That's the bit I can't shake off.
"Every episode I have also leaves a bit of a legacy. Everything we cancel, every relationship that I poison or don't have time for anymore, just makes it a little bit tougher to cope.
"I don't know how to slow that down, make it stop, what to do."
Jones' story mirrors that of former All Black Carl Hayman who spoke publicly for the first time since last year revealing he is living with early onset dementia.
Speaking on TVNZ's Seven Sharp as part of a dementia awareness event 'A Light in the Darkness', Hayman spoke about his life with the brain condition.
The 42-year-old father of four, who played 46 tests for the All Blacks between 2001 and 2007, says he was prepared to live with a sore knee or sore back for the rest of his days after rugby, but to have a medical specialist tell him he had dementia is something he never thought he would need to deal with.
"I've got various symptoms from changes in mood, to forgetfulness to constant headaches. It was pretty much zapping the life out of me really," Hayman said.
"It's been incredibly tough, but it's a matter of accepting that my brain energy is half full compared to other people, so I need to be careful about what I use that energy on. I need to plan my day, not take too much on and have little achievable goals for the day.
"Having that understanding and the tools to help deal with things, has really given me hope to move forward, in terms of having a productive future."
Scott Robertson has resisted any temptation to rotate his side for the All Blacks’ year-ending test against Italy, naming as strong a side as possible for Sunday’s clash.