Jose Mourinho's men continue to be favourites for the English top-flight title, sitting five points clear of Manchester City through 23 matches, and the Brazil international has featured in 22 of them for the Blues.
Willian, formerly of Shakhtar Donetsk and Anzhi, said with three titles still on offer for the Stamford Bridge outfit - including the League Cup and UEFA Champions League - it was a peak period for the 26-year-old professionally.
"I think this is the best moment of my career," Willian told Perform.
"I've been improving, developing my game.
"I am very happy for playing in such a club like Chelsea, which was my dream, having the opportunity of playing in a big league, the English league.
"I came to Chelsea for winning titles and we are close to it this year.
"So I think I am in a good moment, and I put in my head that I can't never feel comfortable, even when I would become a regular don't feel comfortable and try always to improve more.
"That's what I have been doing."
On Chelsea's signing of midfielder Juan Cuadrado, Willian said he welcomed the competition for spots in Mourinho's starting XI.
"Sure competition for a place in the squad grows. But I will always fight for my place," he said.
"As I said, I can't never feel comfortable otherwise another player comes and take my position.
"I need always to improve and that is why I work hard to try and keep my place in the squad. All good.
"He did his first training today, we spoke with him who looks like a calm boy, a good guy. We hope he can be happy with us here in Chelsea."
Chelsea play Tottenham in the League Cup final on March 1, and have a European last-16 first leg date with PSG on February 17, and Willian said they were all on the minds of the squad.
"In our head we want to win all three titles. We have squad for that, we know our qualities," Willian said.
"But we also know how difficult is to win all of these trophies.
"We will face a tough opponent in the Champions League, and if we go through it will be always tough matches in the quarter-finals, semi, and on.
"We also have a difficult opponent in the League Cup, and we are top of the league with five points advantage.
"All we players can do to win as many titles as possible, we will do it. We know how difficult it is going to be so we must be focused and try to win all we can."
