Arsenal defender Laurent Koscielny says they weren't good enough in the final third of the pitch after West Ham beat them 1-0 on Saturday.
Unai Emery's Gunners failed to close the gap on Chelsea, who play Newcastle later today, as Declan Rice scored the decisive goal of the match at the London stadium.
Speaking to Sky Sports after the defeat, Koscielny, who was left upset by the result, said: "I think in the final third we needed to keep more calm and not try to find the final ball and to continue to play with movement.
"In the second half we didn't stop but conceded the goal early. We had some chances and we didn't score. It is difficult to win if you don't score. We need to keep our ambition and our game. We can come back.
"We needed to be clean with the ball and we weren't. In football if you give a small chance to your opponent you pay and today we did.
"When you are arriving towards Christmas you know it is a big period and it is hard to compete at the same level. We started the new year with a win and we prepared for this game and came here with ambition for three points but we need to keep calm and focused on how we want to play.
On facing Chelsea next, the Frenchman replied: "It is a home game against an opponent in the top four. We know what we need to do. We need to prepare all week for this important team."
Arsenal have taken just two points from their past five away Premier League games - they won 13 in the five away games prior to this run.