The Spaniard initially struggled for goals since his €60 million (£50m) transfer from Liverpool, frequently finding himself out of the first team as Didier Drogba excelled in 2011-12.
Torres confirmed to El Pais that he had "not [been] the person I wanted to be", explaining: "I have done lots of things wrong.
|33/1||Fernando Torres is 33/1 with Bet365 to score a hat-trick against Tottenham
"I had many team-mates who didn't care about winning or losing if they didn't play. I didn't want to be like them but there was a moment when I realised that I didn't care either.
"I also realised I was not happy, as I was not the person I wanted to be.
"I sacrificed myself for the team, as it was the only way to play."
Things are looking up now for the forward, however, who added of Blues boss Roberto Di Matteo: "The change of coach has made me a better player.
"I can control now some issues I didn't control in the past."