The Gunners lost 2-1 at home against Brighton and Hove Albion.
Arsenal have slipped down to 5th place in the league standings with last night’s defeat at home.
Earlier this week, Arteta’s men lost against Crystal Palace and lost Kieran Tierney to a long-term injury in that game.
Spurs won 4-0 against Aston Villa and climbed to 4th in the Premier League table and are three points ahead of their North London rivals.
Arteta said: “It has been a tough week; especially today because we wanted a reaction [to the defeat at Crystal Palace].
“It came in the second half, which is too late; we have to have the courage and personality to play much better and raise the level in the first half.
“We made it really difficult for ourselves. We were sloppy, we had no purpose to attack, we were really imprecise and we didn’t want to play forward.
“We’ve shown for many weeks how well we can play; it has been a difficult week and we’ve lost some big players, but if you get what you want, not everything is going to be with a blue sky. This is our team in the good moments and especially the defeats.
“There are many games to play but we have to be concerned about that performance, especially first half.”
