The Portuguese is back at Stamford Bridge after departing the club for the first time back in 2007, signing a four-year deal to lead the Blues for a second stint.
"The plan is always the same, evolution and to establish the club at the highest possible level," he told the club's official TV station.
"I left Chelsea in 2007, since then I've spoken about the club many times, especially in my privacy. I remember the day we went to the United States in 2004 pre-season. We had open training sessions with only a couple of kids watching the sessions, nobody was following the team. It was the beginning of Roman and his second season I suppose was the beginning of Chelsea.
"After that Chelsea started winning the Premier League, for the first time and then the second time, and after that when we went back to the United States we found a completely different situation around the club.
"I can imagine now especially after the Champions League, that was the highest point of the club's history, that this is now a bigger club. The social mass around the club is much bigger.
"I am the same, physically the same, but every day you have to think about yourself, especially the manager, and about the evolution. I have the same nature but I'm much more mature with a different approach to things, I'm more ready to be in a club and stay for a long time."