Mikel Arteta rued Arsenal's loss of purpose after they went 2-0 up against West Ham and then blew the chance of victory.
The Hammers hit back to draw 2-2 at London Stadium on Sunday, in a damaging result to Arsenal's title hopes, with Manchester City now just four points behind with a game in hand.
Bukayo Saka's penalty miss early in the second half was compounded by Jarrod Bowen's equaliser two minutes later, as Arsenal surrendered a two-goal lead for the second game running, having previously done so at Liverpool.
Gabriel Jesus and Martin Odegaard put the Gunners 2-0 up inside 10 minutes at West Ham, but Arteta thinks his team grew complacent.
"Very disappointing. The way we started was superb again, we were in total control, then we lost purpose," he told Sky Sports.
"We gave them hope, conceded a terrible penalty, then credit to them. We got on the roller coaster where everything is going, corners and throw-ins, and we never got away from that.
"The purpose we needed for a third and fourth goal, I didn't see it."
Arsenal's lack of focus was exemplified by Thomas Partey's mistake in the build-up to West Ham's first goal, with Declan Rice robbing the midfielder of possession before Lucas Paqueta drew a clumsy challenge from Gabriel Magalhaes.
Saka ultimately missed the chance to restore Arsenal's two-goal advantage when he skewed well wide from the penalty spot following Michail Antonio's handball, but Arteta was philosophical about the youngster's profligacy.
"A player who takes penalties misses penalties, I don't know anyone who hasn't," Arteta said of Saka, before adding Arsenal "can't control" the pressure in the title race.
Captain Odegaard echoed his manager's thoughts, saying: "A lot of the same things to last week – started well, but then we stopped, allowed them to play on their qualities.
"We gave them the game they wanted, we gave them hope, and that's on us. We have to look forward now.
"We started to do a lot of stupid things on the ball, we allowed them to play on the long balls.
"We have to remember we are still top of the league with everything in our own hands. The same mindset, same mentality to make sure we win the next one."
Arsenal will look to bounce back against Southampton on Friday, before they face City in a potential title decider on April 26.
West Ham, meanwhile, are now four points clear of the bottom three.
"It would have been a good result getting a point anyway, but going 2-0 down and coming back shows great character," Hammers boss David Moyes told BBC Sport.
"The games are coming thick and fast and the players are doing a really good job."