Guy Sebastian has revealed his lack of self-confidence almost stopped him from chasing his Idol dreams back in 2003.

He opened up about Australian Idol on the latest episode on Anh's Brush With Fame, explaining that he didn't think music would be a career option for him to host Anh Do.

“I wasn’t sure music was an option for me,” he told Do.

Sebastian recalled a particularly disheartening trip, where he was repeatedly told by music industry figures that they loved his voice but not his look.

“I was a weird-looking chubby, half-Asian kid who didn’t have the pop star look. I got on the train with all these rejection letters, tail between my legs and thought, I can’t change how I look, but I can still be a musician,” he recalled.

“I’ll just write songs for other beautiful-looking people; that was my mindset.”

Sebastian noticed an audition sign for the first season of Australian Idol, but wasn't confident about his chances.

“I thought, ‘As if I’m going to win a TV show, let alone get a record deal’. I’m going to go on TV with all these beautiful pop star-looking people? I’ll never win.”

Luckily, Sebastian nailed the audition that left judge Marcia Hines visibly moved. Judge Ian "Dicko" Dickson wasn't impressed and said that Sebastian looked "crap, so we're going to have to work on that".

Dickson's comments are still in Sebastian's mind 18 years later as he remembers that moment vividly.

“That insecurity that was starting to dissipate came back. I thought, ‘Maybe I do look like crap, I’m not cut out for this.’”

However, he kept pushing on and has carved out a career in the Australian music scene.

“I knew I was lucky, so I knew that would be frustrating for a lot of people who have really slogged it out trying to get into the scene. I’ve been given this opportunity through Idol — people voted for me. Kids went into debt voting for me! I’m forever in debt,” he said.

“That’s why I keep going, because I was gifted this amazing opportunity. It’s a weird way to enter the industry, but it’s given me a fire that’ll never die out, because people believed in me.”