Faria, a centre-back on loan to Rio Ave, struggled to stem the flow of tears as he told reporters that, because of a heart anomaly, he was forced to seek alternative employment.
"This decision really pains me but I had the support of my parents, girlfriend, Benfica, Rio Ave, my agent and also from the players' union," he said. "That's life. The last exams did not go as well as we hoped for."
Faria's problem was first detected after a league match in February last year and he had not played since.
Benfica president Luis Filipe Vieira, who sat by his side in the press conference, said Faria could count on his club for help.
"He can count on Benfica, he won't be unemployed. We have a contract with Faria until 2015 and we will keep to it. Benfica's door will remain open," Vieira said.
Faria did not specify what his exact condition was.
"I realised I had to stop after some tests with physical exercise. It's a heart problem but I am not really able to explain you what it is," he said.
Former Bolton Wanderers player Fabrice Muamba suffered a cardiac arrest and almost died playing at Tottenham Hotspur last March.
Muamba, whose heart stopped beating for 78 minutes after collapsing during an FA Cup tie, made a full recovery but was forced to retire from the game on doctors' orders.
A few weeks later Livorno's Piermario Morosini collapsed and died from a suspected cardiac arrest during an Italian second division game.