Arsenal manager Arsene Wenger was left bitterly frustrated after his side let a lead slip for the second time in six days as they were held 2-2 by West Ham.
The Gunners, who saw AZ Alkmaar come back from a goal down to draw 1-1 in the Champions League on Tuesday, were 2-0 up against West Ham at Upton Park.
"It's very sickening because it doesn't reflect the quality of our game," Wenger told BBC Sport.
"We need to learn from our mistakes and the quicker the better."
The draw sees Arsenal leapfrog Tottenham into third on goal difference but a win would have seen them move three points behind leaders Chelsea with a game in hand.
Wenger's side took the lead through Robin van Persie and the Dutchman then turned provider as his corner was headed in by William Gallas to make it 2-0.
"We played very well in the first half and we have to keep the positives of our game," said Wenger.
The Gunners appeared to be cruising towards victory but West Ham rallied in the second half and appeared to grow in confidence as the visitors squandered a number of chances to finish them off.
After Abou Diaby fouled Zavon Hines, Vito Mannone could only parry Alessandro Diamanti's fierce free-kick and Carlton Cole headed home.
West Ham then equalised as Alex Song felled Cole in the penalty area and Diamanti lashed home the resultant spot-kick.
"It (the free-kick on Hines) was a very generous decision," Wenger argues. "The penalty was super generous.
"It was a very physical game with a lot of fouls made on us. But we had plenty of opportunities to score a second goal but we didn't and we have to learn.
"We shouldn't have even have been tempted to give away a free-kick for their first goal."
We fought until the end - Zola
West Ham's comeback follows Alkmaar's in midweek, when David Mendes Da Silva struck late on to cancel out Cesc Fabregas's opener and earn his side a point.
But Wenger rejected suggestions that Arsenal's recent failure to hold a lead was down to any deep-rooted problem.
"There is no lethargy, the team wants to win and it focused," the Frenchman insisted. "There's no lack of concentration.
"When you lead 2-0 away the game is never won. West Ham fought for their life, they never gave up. When a team never give up you know they can come back.
"We had it in the Champions League but this is more sickening."
West Ham boss Gianfranco Zola admitted to doubting whether his side could get back into the match at 2-0 down but was full of praise for the way they responded.
The Italian introduced Hines and Diamanti in the second half and both players played a large part in turning the match on its head, while Cole was superb throughout.
I have 'killer instinct' - Cole
"Never say never," Zola commented. "The reaction surprised me because it was looking pretty bad for us.
"But at half-time we had a chat and and said the only way to react is to fight to the end. They did and it turned out to be a great point for us - it feels like a victory.
"The substitutes were great and the crowd were like a 12th man on the pitch.
"That is Diamanti - we know he is capable of those things - but also Zavon was alive and made a great contribution. We need everyone's best performance now and to come off the bench and do that makes a big difference.
"Today we got a point that I value at three points. No one will give you anything in this championship - you need to perform at your best."
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