Nainggolan has attracted enquiries from Chelsea for the past two seasons.
“I could have gone to Chelsea, but also other teams," Nainggolan told SportMagazine.
“But at 28 or 29, to go somewhere else, with a new culture and a different lifestyle… there's nothing in that for me. I prefer to stay where I'm happy
“If money had been my motivation, I'd have changed clubs several times, my wages would have gone up several times. My main motivation is living well.
“You have to be happy, and you have to be happy playing where you are. I have both things here, everything is perfectly matched.
“My family are doing well here, there are a lot of good restaurants and it's a nice place to shop. If friends or family come to visit, you can send them anywhere.
“I'm also tied to the club, the fans are behind me. I've given a lot on the pitch and I get a lot of respect for that. As a footballer it's one of the best feelings you can have."