Further to the theme of my previous post, the book by Professor Paul Helm has been helpful to many. In The Callings (a Banner of Truth paperback) has some sound advice for Christians. Paul Helm believes that many Christian's lives have been harmed by thinking that the only worthwhile way to live is in some kind of 'Christian' career. In fact God 'calls' the vast majority of Christians to serve him in the occupation that they are in. This book shows that instead of dividing life into 'spiritual' and 'secular' compartments, every moment of it can be lived fully to the glory of God.
Highly recommended!