The 23-year-old netted a second-half hat-trick to help win the west London derby 3-1 at Fulham, which sent Mourinho's side four points clear of the chasing pack.
It was a first Premier League start of 2014 for the £18million summer signing from Bayer Leverkusen.
Schurrle accepts it was always going to take time for him to adapt to the hustle-and-bustle of English top-flight football - which has included plenty of work on building up his physique.
"We (Mourinho and I) talked a lot, of course. He told me I needed to change, to change my game and my body, and that is what I have done over the last two months," said Schurrle, who was set up for two of his goals by the brilliance of Belgian starlet Eden Hazard.
"I have really worked very hard to be aggressive, to be in a good shape with my body. Now I'm ready to play more often.
"I did a lot in the gym, but I wanted to do this, I needed to do this.
"The manager told me it as well, I wanted to change and I think I have."
Schurrle looks set to be part of Germany's World Cup plans this summer having bagged a hat-trick in the qualifiers against Sweden.
The 23-year-old wideman is confident he can bring plenty to the table for club and country.
"I think I am more of an attacker than a midfielder like Lamps (Frank Lampard). I can play 'number 10', on the right side or something in between to get my runs into the deep and get some shots in," he said.
Chelsea could move further ahead at the top next weekend, given Manchester City and Arsenal are both involved in the FA Cup quarter-finals.
Schurrle said: "We have to believe it. I think everyone believes it now. We have worked hard for this.
"We have to keep going, keep winning like we did at Fulham, then we will see at the end."