The centre back earned his first France cap last month and believes his Cup Final experience eventually put him on the right path.
"I do think about it sometimes," Koscielny told the Official Arsenal Magazine. "Mistakes can happen in life.
"It was hard for the fans and for the Club but life goes on. There are things more important than losing a Final. There will be plenty more finals to play and win.
"It was tough to swallow but it made me a better player and a better person.
"Afterwards I had a week where I was feeling really bad. It was my first Final and the Club and the fans had been waiting for a trophy for a while.
"It was so hard to take. I needed time to digest it but I had to bounce back to come back stronger than I did."