The Gunners are recovering from their home defeat to Swansea City on Saturday.
The Pole told supporters: "Even after a game like that when everyone is disappointed, the fans are disappointed, the players are disappointed, it is very easy to give up and just say that we are not good enough.
"We definitely believe we are good enough to do the job, we are going through a little bit of a rough time but just keep the faith and I'm sure sooner rather than later, we will get there.
"It is very hard right now. This defeat is even more disappointing because we played at home against a Swansea side in a game you should be winning comfortably when you play for this club."