The Australian actress, who currently stars in Judd Apatow's comedy movie Bridesmaids, said that she feels like she now has control of the panic attacks that she used to have on a regular basis.
Byrne told The Daily Telegraph: "I'd feel like I was going crazy, like I was completely losing my grip on reality. I'm a lot more relaxed now. A few years ago in Sydney I took a course in how to deal with panic attacks and that was a big turning point for me.
"I still get anxious but when I do I know how to control it a bit better. If I'm in a crowded place I immediately feel anxious."
Byrne also revealed that she auditioned for Home and Away but "failed to get [her] rite of passage" on the show. "I eventually got onto a soap called I," she said, "but it was cancelled."
The Damages star described herself as "young, wild and foolish" when she first started her acting career, saying: "I'd sneak out of the window and go to all-night parties. I once gave a guy a black eye for spurning my advances".
Byrne co-starred with Russell Brand in Get Him to the Greek and described it as a "challenge". "You never know how he's going to be," she admitted. "You're working with someone who's had many colourful incidents. Yes, he's eccentric, but I would work with him again in a heartbeat."
Bridesmaids is released in UK cinemas next week. It entered the US box office in second place last week and rumours of a sequel to the film have already surfaced.
Watch the Bridesmaids trailer below: