Jarrod Bowen struck for the Hammers as they won 1-0 on Saturday, with the Gunners seeing Myles Lewis-Skelly sent off.
Arteta conceded afterwards, “First of all, congratulations to West Ham for the victory. We’re very disappointed with the result and as well the performance for the last period of the game because we really wanted it and showed that we really wanted it, and it becomes really difficult with 10 men.
“Today, we were not at the levels and standards that we have to hit to be much better than the opposition.”
He also said, “We have to go through the pain of defeat and a big part of the performance as well.
“That’s what we’re going to need on Wednesday (against Nottingham Forest), to put in a different performance and win the game.
“Let’s go through the pain; let’s analyse, look at ourselves in the mirror and on Monday we go again.”