The singer’s latest album, 21, is at the top of the charts in Britain and the US, but she said she refuses to let her achievements go to her head.
She told the Daily Star: 'In America people knew who I was before I sold any records. I always felt really welcome there. However, nothing really sinks in with me - you do have to put a bit of a wall up and let things pass you by. I would melt into a puddle if I thought about it, or become a massive arsehole.'
Talking about the album, which was inspired by a break-up, she added: 'I like pouring my heart out on record as I find it comforting. It feels a bit anonymous when I've put it in a song and it's very cheap therapy - I didn't have to pay £1000 a session.'