Ivanovic joined Chelsea from Lokomotiv Moscow two years ago and made his 50th appearance for the club in the win over Sunderland.
The centre-back was long linked with a move away from Chelsea and clubs such as Real Madrid showed their interest in the 25-year-old.
“For me the long period in the last two years was when I arrived here and there were problems,” he told Chelsea’s official website.
“After that I started to play and at the moment I feel very comfortable and happy.
“When I started to play I was very happy because I play with great players in a great team and now I start to give my best.
“I didn’t count my games but of course it is good for me to play 50.
“I tried to improve in these games and that I have played 50 games surprised me a little bit.
“Now I try to come to 100 games as soon as possible, quicker than to 50.”
“I think I improved my language when I started to play,” said Ivanovic.
“It was very hard for me when I arrived and I didn’t speak easily. At the moment I think I can speak and I understand a lot of things, but I have to learn more.
“It is important for every player to feel comfortable.
“We have a good atmosphere and you can improve with these guys.”
