Madonna lives a very ''disciplined'' life.

The 57-year-old singer has admitted she doesn't tend to socialise with her friends because she'd rather focus on her career and stay in shape to benefit her career.

She said: ''I have a very disciplined life. I don't do a lot of socialising. My life revolves around my show and my four children and trying to live a very healthy lifestyle.''

However, the blonde stunner - who is mother to four children, Lourdes, 19, Rocco, 15, Mercy and David, both nine - has admitted she feels exhausted all the time.

She explained: ''The only thing I'm lacking now is sleep.''

And it's not wonder as Madonna is currently on her 10th world tour but has admitted she's struggling to put together a unique experience because she's been doing it so long.

She said: ''It's hard to choose. Sometimes I have to let go of things I love because they don't sound right or go with the theme. Or I go, 'Oh I did that the last three shows. Even though I love that song let's do something new.' ''

The 'Ray of Light' hitmaker even has to drop her favourite songs in favour of what she knows her fans want to hear.

She told Britain's HELLO! magazine: ''I tend to like my more abstract, less commercial songs, but I realise I have to have songs that people are familiar with and want to sing along to. So I have to balance it out and not just do a creative show that is going to please me.''