The 28-year-old arrived with a big reputation, having won three Heineken Cups with Leinster, but Sexton believes that arriving in Paris as an overseas player has forced him to raise his game.
"You know, as a home-grown boy in Leinster I used to judge the foreign players when they signed for us," Sexton told the Telegraph.
"Did they really want it? Did they put enough in? Guys like Isa Nacewa, Felipe Contepomi and others did. Some did not. That has stayed with me.
"You have got to make an impression. I work hard, I train hard. That's why I hope I'm showing the Racing supporters that I have this burning desire to succeed, to help make this club a real force.
"I am out of my comfort zone and I have to get on with it. Of course there is pressure on me as the high-profile signing and I am uneasy with that tag. It is up to me to deliver."