Madonna ''doesn't do a lot'' of socialising because she needs to focus on her work. The 57-year-old singer thinks it is essential she is ''very disciplined'' and stays focused on her career in order to stay in the shape required to cope with her strenuous stage shows. 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. ''The only thing I'm lacking now is sleep.'' Madonna - who is mother to four children, Lourdes, 19, Rocco, 15, Mercy and David, both nine - is currently on her 10th world tour and admits as time goes on, it become difficult to put together a unique concert experience and she often has to ditch something she loves, just to refresh the production. She admitted: ''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.' '' And the 'Ray of Light' hitmaker 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. ''I have to be quite brutal sometimes. It's kind of like editing a movie because there are scenes you love but they just don't help tell the story and you have to let them go.''..