De Bruyne scored 10 goals in 33 appearances for the Bundesliga side, and the Belgian international believes that he has benefited from gaining a full season of first-team football under his belt.
The 21-year-old told the club's official website: "We had a difficult season with a lot of really young players who had almost no experience in the league, so it's very difficult.
"But I felt that I had a good season and played a lot of minutes, and also with the national team which was very important for me.
"I think I managed to have a good year and managed not to have my own injuries, so I was very happy."
De Bruyne will remain at Chelsea this season, despite interest from Bayer Leverkusen and Borussia Dortmund.