The Giallorossi sold the Brazilian over the weekend for a massive €31.5 million.
"I chose PSG because they presented this wonderful project to me. It's a great club with excellent players and I'll mature a lot with them," he told Lancenet.
"I must keep my feet on the ground when people tell me I'm the fourth most expensive defender in history. It's just a matter of personality and how you were brought up, as in football it's easy to lose sight of the situation.
"The interest from so many clubs came about because I worked hard and I must continue to prove my worth every single day.
"I had a marvellous experience with Roma, even better than I expected it to be. I arrived with a great deal of humility and a little confusion, as I was leaving Corinthians after 10 years to face a different language, city and culture.
"I felt a bit lost, but adapted quickly and have grown up thanks to Italian football. In Paris I'll take the same approach, trying to earn my spot with humility and hard work. Nobody expected me to grow so quickly at Roma."