I agree good self education is the key. Knowing real reasons WHY you don't want drugs i.e. having a real motivator rather than, just because, and having great support and preparation of how you might feel and what you can do in a 'crisis of confidence'.

If you don't have a real convincing reason in your own mind why you don't want drugs, when you are in the throws of labour, what is going to hold you to it?