Chelsea striker Diego Costa says boss Jose Mourinho wants his players to be mentally strong.
The Blues endured a very disappointing start to the campaign as they struggled in both the Premier League and Champions League.
But the 27-year-old says the atmosphere in the dressing room is "great" ahead of the weekend game against West Ham United.
"Things aren't going so well for the team right now, but it's not because of the changing room," Costa told the BBC.
"The atmosphere is great. During the year I've spent here, there hasn't been one argument. There are normally disagreements in all changing rooms, but it hasn't happened here.
"Before the season started, the coach warned us.
"We had a meeting with him and he warned us about our mentality.
"Our coach is very clever - he saw the situation we are in at the moment before it happened."