I think this is a really wise mindset. I was quite similar, in that, I go into all my labours with an open mind and the realisation that if I -need- pain relief, I will have it.
I'm also a huge believer in praying specifically about the kind of birth you would like. I've been fortunate enough to have 2 short labours (DS 6 hours, DD 3 hours) and both were totally drug free.
Often it's the fear of the pain that can make it more painful for us, read up as much as you can on different forms of pain relief (including natural forms) and different positions to labour in. I gave birth to both my kids standing up and I highly recommend it!!!!
The other thing to remember, is that you are NOT a failure if you do have an epidural or any other form of pain relief.
While I totally support natural drug free births, I know that not everyone has short labours like mine! And the worst thing we can do, as women, is feel guilty for the choices we've made in terms of how we handle pain etc.