Tottenham simply have to put in the hard graft as they look to salvage something from what is turning out to be a disappointing end to the campaign. (More Football News)
Spurs' Champions League hopes appear to be fading fast after they lost for a third straight game in the Premier League, going down 2-0 at Stamford Bridge on Thursday.
Tottenham have four games remaining, albeit that includes meetings with Liverpool and Manchester City, and they are seven points behind fourth-placed Aston Villa.
They were particularly vulnerable from set-pieces once again, with both of Chelsea's goals coming from such scenarios.
Asked how Spurs can turn it around, Postecoglou said told BBC Sport: "Just hard work mate, there's no major formula. We will work hard and make sure we get it right."
He added: "It wasn't a great night for us. We didn't play at the levels we needed to and didn't deserve something from it.
"We lacked belief and conviction in our game. I don't know if it is low confidence but we are not playing with the mindset we need to play the football we want to and that is something I have to look at.
"It is on me to fix it. That is what we will be doing. We had bigger issues tonight than set pieces."
Speaking to Sky Sports, the Tottenham boss said: "I feel like we've lost a bit of belief and conviction in our football and that is on me to change that.
"It wasn't about conceding the [first] goal, it was our approach to playing football and we were nowhere near good enough. That is on me.
"We've been in a bit of a grind for a while now, that is part of our challenge and part of our growth. We have to go out there and perform and sometimes you have to grind out. We were poor today."
Spurs defender Micky van de Ven, meanwhile, conceded Champions League qualification looks out of sight.
"It will be difficult. I don't want to look up to the Champions League after this game, it was not a good performance from us and it is important we play a good game on Sunday," he said.
Mauricio Pochettino, meanwhile, became the first manager to complete a Premier League double over Tottenham having previously managed them in the competition.
Chelsea are up to eighth, just three points behind sixth-placed Manchester United.
"So happy and so pleased. So happy for our players," Pochettino said.
"The first half was fantastic. Then you have to contain and suffer. Tottenham have quality players. Not too much to say, all credit to the players."
