Tottenham boss Antonio Conte says it is "impossible" for a team hoping to fight for the Champions League places to lose games the way Spurs have recently.
Sunday's 2-0 loss at home to Wolverhampton Wanderers was Tottenham's third Premier League defeat in a row.
It leaves them eighth, five points off the top four, albeit with three games in hand over West Ham in fourth.
"I am telling you from my arrival that we have to struggle every game," said Conte, who took charge in November.
"There are a lot of jobs to do but it is not simple because the environment is used to play for Champions League, Europa League, but everyone maybe has to realise something has changed and you have to try to work to build again and we have to know this."
Speaking to Sky Sports, Conte added: "When you lose two games in a row at home and a previous game against Chelsea, a team that wants to fight for the Champions League is impossible."
Tottenham went unbeaten in nine Premier League games following Conte's arrival.
But the Italian says it will take time to develop a side capable of believing it can win regularly.
"The problem is that you cannot buy the winning mentality," he said.
"You transfer it day by day and [you are] not sure that [it is] day by day, because there are players that are more open and they understand the process quickly, other players need more time to understand this.
"Winning mentality in my opinion means when you play, [thinking] 'I am ready to kill you and to live'. This is the difference in every duel, every second ball, every set-piece.
"There is a long road, a long path in front of us. Long. It's important for us not to be scared to face this path."
