The 46-year-old Australian actress, who is best known for playing Julie Rafter in the Seven network family drama Packed To The Rafters, said that she used to have to take a Valium pill and put on a "mask" to even be able to leave her home.
Gibney told Mindfood magazine that despite her career success 15 years ago, she was in a very different place emotionally to where she is now.
She said: "I didn't have self-belief... I didn't believe in my acting ability, I didn't believe I was that good-looking. When you're in a black hole, when you've been in the pit, you don't want to go back there. And I'm so glad that rage is gone… that intense rage."
Gibney also revealed that although she still suffers from the occasional panic attack now, she knows how to handle them.
Last year, Gibney told Australian Women's Weekly magazine that she had "a complete emotional collapse" because she was full of "self-loathing".
Packed To The Rafters was recently taken off-air until later this year.