The Pole kept the Gunners in the game on Saturday before Michu's late brace won it for Swansea City.
"I admit it has been a difficult few months," he told arsenal.com. "I found it hard to adjust playing with little injuries and knocks, especially in the last couple of months of last season.
"But I am pretty much sharper and fitter now, looking forward to getting back to my best and leaving those difficult times behind.
"I am feeling really sharp in every game, and the manager is sticking with me, which is really good, so I just want to get back to my best as quick as I can because I have not been at my best for the last few months."