Mason suffered a fractured skull after he and Cahill clashed heads in January 2017, and despite doing everything he could to get back in the game, he has had to retire amid concerns about his safety.
"It's been quite sad and emotional but at the same time I've had so many good luck messages and positive feedback from my career that it has been nice at the same time," he told 'BBC Five Live' on Friday.
"Throughout this last 12 to 13 months it has been a constant battle, but I was always confident that I could get back out on the football pitch. But it was probably a week, two weeks ago that I got some pretty conclusive and strong news," he added.
"I've actually been fit and probably waiting really for six or seven months to try to get back out onto the pitch and if someone did give me the all-clear then I probably would have felt pretty confident fitness-wise to go straight back into it."
"But when it is something so sensitive, with your brain and your skull, it does probably make it a little bit easier to accept you are not going to play again, because it could be life-threatening," he did concede. "[Although] I'm looking forward to the next chapter."
Despite the unfortunate news, things are looking up for Mason as Tottenham head coach Mauricio Pochettino has offered him a job at the London club.