Raya proved himself with the Gunners, though concedes his shaky start after joining from Brentford had him questioning himself.
The Spain goalkeeper has won the Golden Gloves for the past two Premier League seasons, but his form was always solid.
He told Fozcast: "It was a turning point against Luton. That game was one of the worst games I ever played and that's where I hit rock bottom.
"From there, the only way was up with changing my habits and trying to change my mindset.
"From that game, I said, 'Listen, this is not me.' I think there's been a massive change from there."
Cana impact
Raya was eager to highlight the influence of Gunners goalkeeper coach Inaki Cana.
He added: "I met with the goalie coach after the game at the training round and we were there for two hours, talking about things that we could change.
"He helped me a lot in that situation and he just believed in me. We had to change things.
"(I was) working with him, working with a sports psychologist and relying on my missus and my family to try to help me as much as possible. That's when I started feeling better."