Midfielder Barton was part of the Everton academy from the age of seven to 14, but was told he was not big enough to continue on at the club.
The 34-year-old was talking in the September edition of FourFourTwo magazine, where he revealed the mindset he was going through at the time of his release.
“It was an incredibly difficult time,” said Barton as quoted by the Liverpool Echo (8.28am).
“I was a boyhood Evertonian, standing on the terraces and waiting outside of the training ground for autographs.
“After being in the academy from the age of seven to 14, to be told that someone has decided you’re not big enough – not that you’re not good enough – is tough.
“But you either mope and confirm they were right, or you say: ‘I’m going to prove you wrong.’ I think I’ve validated that I was right and they were wrong.”
The aggressive midfielder is currently playing for Rangers in the Scottish Premiership, where he is hoping to help Mark Warburton’s side win the SPL title following promotion last term.
Barton has played for Manchester City, Newcastle, Queens Park Rangers, Marseille and Burnley in a successful career spanning 14-years so far in three different countries.