The 24-year-old made more than 300 appearances for the Gunners, scoring 59 times, after being plucked from the Camp Nou club's youth team by Arsene Wenger in 2003.
But despite being part of the side that won the FA Cup in 2005, the Spaniard was unable to guide the Gunners to more trophy glory.
And after a sixth successive campaign without tasting success, which included a last-gasp loss to Birmingham City in the League Cup final, Fabregas says the time was right to move on and attempt to win honours with his star-studded hometown team.
"I thought it was the right moment. I'd given everything for Arsenal," he says in the January 2012 issue of FourFourTwo magazine - out now.
"I played with a broken leg, I played when my grandfather died. I gave everything but you reach a moment when you say: 'I can't give any more'.
The former Arsenal skipper is keen to dispel theories that he took "the easy option" by joining a team possessing the talents of Lionel Messi, David Villa, Andres Iniesta and Xavi.
Instead, Fabregas sees it as his toughest challenge yet, to become a permanent fixture in a side that was won the Champions League in two of the past three seasons.
"I think I took the hardest option," he says. "I'm competing with the best central midfielders in the world."
Read the full in-depth interview with Cesc Fabregas in theJanuary 2012 issue of FourFourTwo magazine- out now - which goes inside QPR with Tony Fernandes, Neil Warnock and Joey Barton.
It also features the release of the annual 100 Best Players in the World, with Samir Nasri, Daniele De Rossi, Yaya Toure, Edinson Cavani and Manuel Neuer among those interviewed.Subscribe now!
NEWS:Nasri - We knew Cesc was leaving Arsenal
Get the best features, fun and footballing frolics straight to your inbox every week.
Thank you for signing up to Four Four Two. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.