The Gunners have rallied with eight wins in their past nine matches in all competitions and Koscielny believes a new-found team unity can continue to push the North London outfit forward.
"There is a new team spirit at the club. We are all fighting for each other, we are all united," he told the club's official website.
"Everybody defends. If you just defend with the four defenders, it's difficult. But now we are a real unit and it's easier. The new players have now adapted well to the team and to the football we play.
"We have gained more serenity too. At Chelsea (5-3 win), even when we were a goal behind, I knew we would win. We have improved so much in the last month and we have players in great form like Robin (van Persie).
"We all became aware that we could achieve something great this season. This team is growing and so am I."