The French centre-half has taken a while to settle at the Emirates Stadium but is starting to come into his own with some assured performances in the back four for the Gunners.
Koscielny says he is becoming better at coping with the pressure which comes with the territory at a club like Arsenal and also feels the weekend's 5-3 win over Chelsea will do a lot to help confidence on the red side of North London.
"I feel I'm in the best form of my life," Koscielny told the club's official website. "I've improved a lot. I keep working on the basics, my controls and my passes.
"I'm also more rigorous. I make less fouls and get less booked as I needed time to adapt to England. I also cope better with the pressure of playing in a very big club. And I know I can improve even more.
"Chelsea was one of the best performances of my career, along with the win against Barcelona at home last season. Most importantly it's a win that will bring the team together even more and will bring great confidence."