Arsenal manager Arsene Wenger praised his team's resilience after they hit back from a goal down to beat West Ham United 3-1, but also admitted that they worry him.
After dominating the first half at Upton Park, Arsenal fell behind to a goal from Carlton Cole, but fought back through a Theo Walcott brace and a strike from Lukas Podolski.
"I have confidence in the team, but I also worry," Wenger said. "That is the nature of the game. You always worry.
"I am proud of the character of this team because they are always focused and try to do well. They respond, but football is football."
Arsenal's response, when their heads might have dropped, suggested that they are made of sterner stuff this season than in some previous Premier League campaigns.
"We couldn't take our chances in the first half and we responded very well in the second half, in the end winning the game in a convincing way," Wenger said.
"The positive is we created chances. The negative is we didn't take them. Sometimes there is a guilt flying around the team when you don't take your chances. You think, basically, we deserve to be punished, and we were."
One negative for Wenger was an injury sustained by Aaron Ramsey, one of the few players this season who has looked like giving Liverpool's Luis Suarez a run for his money in the Footballer of the Year voting.
"It looks like a thigh strain," Wenger said.
"For me, a thigh strain -- I don't know how serious the thigh strain is -- but the Christmas period is certainly over for him. It was his (23rd) birthday today (Thursday)."
But a big plus for Wenger was the return from a hamstring injury of Podolski.
The German attacker replaced Ramsey after 66 minutes and provided the left-wing cross from which Walcott headed in his second goal of the game, in the 71st minute, before scoring the third himself.
"He has been out for four months, he has not played one game," Wenger said.
"I try to get him slowly back to competitiveness and he has shown that he can have a huge impact because he can score and make you score goals, give assists."
While Arsenal were returning to form, West Ham have now won only once in 11 games, but their manager, Sam Allardyce, took heart from his team's display against the title contenders.
"We had a great opportunity to win against the top-of-the-league team and unfortunately we didn't take it because we didn't get the second," he said.
"We paid the price today, sadly. It is about performing like that against those clubs which give you a better chance to win the game.
"When we've had that opportunity recently, we haven't done that. We haven't played as well as that, apart from when we beat Fulham 3-0 here.
"We played Sunderland here (drawing 0-0) and never got to this level so ended with a draw. We played against Aston Villa at a high level (drawing 0-0), but didn't score.
"We played at Crystal Palace and lost (1-0), failed after going 1-0 up against Norwich (losing 3-1).
"They are key letdowns. You can always lose to Arsenal if you play your best or not.
"It is disappointing for the lads when they have put such a big effort in and made so many chances against this team and have not finished the game off. West Brom on Saturday (at Upton Park) is becoming a must-win."
"Catch-up is getting a little wider and wider each game when you don't pick up points.
"But we have to take a lot of positives out of the way we played today and make sure we play as we did today and like we did at Tottenham in the cup (winning 2-1, in the League Cup quarter-finals), against West Brom."