Nasri was slammed in the media - and by former manager Roberto Mancini - for his poor form in the first-half of last term.
He told FIFA.com: "I feel good at the moment. I'm feeling more relaxed, but the last few months were very trying for me.
"Emotionally, I went through several moments of doubt and reassessment. Some of the criticism I got hurt me, and lots of bad things were said.
"I accept criticism as long as it's justified, but there were lots of lies about me. I made mistakes, I know, but I'm not the ugly duckling that some people seem to think."