The Gunners lost for the first time at the Emirates Stadium in the Champions League on Wednesday night with a 2-0 defeat at the hands of Schalke 04 thanks to goals from Klaas-Jan Hunterlaar and Ibrahim Afellay.
The defeat comes off the back of their 1-0 loss at Norwich City in the Premier League, and Bould feels that his side have lost momentum.
"We haven't played anything like I know we can," said Bould. "We lack a bit of confidence. But it's a tough competition and they're a good side – they beat Dortmund at the weekend. We spoke at half-time about the problems we were having – and for a while it looked like we might get away with it.
"We looked jaded, I don't know why that is. Since the international break we haven't looked ourselves. It's not what we want, it's not what we're accustomed to. We're used to creating lots of chances. Maybe we've lost momentum. We've gone behind in our last five games, so scoring first in the next game is important.
"We still have nine points to play for: How we get those points it doesn't matter, but we'll perform better than we did tonight, that's for sure."
Arsenal host Queens Park Rangers in their next Premier League match on Saturday.