Eden Hazard admits Chelsea lacked motivation last season and says the Premier League champions will be "in trouble" next term should they let standards slip.
The Blues, led by boss Antonio Conte, have recovered from a disappointing 10th-place finish to reclaim the title won under Jose Mourinho in 2014-15.
Chelsea's form tailed off so badly that Mourinho left the club in December 2015 and was replaced by Guus Hiddink as the defending champions briefly flirted with relegation.
The 26-year-old Hazard hinted "motivation" and "fitness" may have played a part in the club's slump but the former Lille winger is determined to learn from the experience.
He told BBC One show Football Focus: "That's football. Sometimes you are on the top, two years ago we won also the league, but last season was difficult for some reasons.
"Sometimes motivation is not on the top, fitness is not on the top, so a lot of things.
"(This season) we started well and we won the league, but next season we will be in trouble if we don't work hard like we did this season.
"We need to be ready every year in the same level to be on the top."
Chelsea secured this season's Premier League crown with a 1-0 victory over West Brom on May 12 after leading the table for much of the season.
Major celebrations have had to be put on hold, however, with the Blues set to take on Arsenal in the FA Cup final on May 27.
Hazard has returned to his best form under Conte, scoring 15 Premier League goals this campaign, and is determined to finish a fantastic season in style.
"We can't celebrate a lot because we have the FA Cup final, we have to be ready for that, but after West Brom we did a little party together," Hazard said.
"Even in the dressing room, it was good to see the smile on faces. I think at the end of the season we deserved to win this title.
"It's not just me, the whole team, all the players they have been fantastic. We won a lot of games.
"We have one more game (against Sunderland on Sunday) and the FA Cup final to play. I hope we can win the double."