The Scottish singer stunned the talent show judging panel of Simon Cowell, Piers Morgan and Amanda Holden with her rousing rendition of I Dreamed A Dream from Les Miserables in 2009.
She finished runner-up on the show behind dance group Diversity and went on to sell millions of records and earn two Grammy nominations.
Despite her success, Boyle, 57, told The Sun newspaper she is still living in the house in which she was brought up in Blackburn, West Lothian.
And the singer, who revealed this week she is releasing an album to mark a decade in music, said she now feels ready for fame.
She said: "I'm managing things a lot better now. It was a slow process. Everything is with me.
"But I'm coping inside a lot better now and I'm ready - more than ready - for what's coming."
Boyle was diagnosed with Asperger's in 2013. She believes it is easier to discuss mental health now because there is more understanding of the issue.
She said: "It can be difficult to talk about mental health issues, as there is a kind of fear about that.
"Years ago there used to be a stigma about it but now there is more knowledge, more expertise, and talking about things makes it a lot easier. A lot easier."
Boyle is through to the final of America's Got Talent: The Champions, a special version of the programme that brings together previous winners and stand-out acts from editions from around the world.
She is joined by her fellow Britain's Got Talent graduate Paul Potts and a winner will be crowned on Monday.