De Bruyne was sidelined after injuring ankle and knee ligaments at the end of January and City slumped to four defeats and a draw in seven Premier League games without him.
"I know the team has a lot of quality but this season has been too much up and down, we've not been consistent on a good level and that's the main issue as to what's happened," De Bruyne told British media.
"I tried to prepare myself, train very hard to be fit... I'm trying to maintain my physical level to be as quick as possible on a perfect level."
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City take on PSG in the first leg of the Champions League quarter-finals on Wednesday and De Bruyne indicated they would look to attack the French champions, who eliminated Chelsea in the previous round.
"In the Champions League, maybe it was difficult in the beginning so afterwards we did well and hopefully we can carry on," he added.
"I think our team always creates chances, I think we are not a defensive team... If the team plays at its best then we always have a chance. If you want to win it then you have to win against the big teams also."
(Reporting by Simon Jennings in Bengaluru; Editing by Peter Rutherford)
