How do I trust my body during labour?

I am currently 28 weeks pregnant with my second baby and I would love to have a natural child birth without pain relief.

When I was in labour with my daughter (who's now 20 months), I managed to get to 6cms with no pain relief, just by walking through the contractions and getting in a bath. I was taken up to the delivery suite, panicked that I couldn't do it any more and had gas and air and pethedine. Labour then slowed down and I'm not sure if it was the effects of the pain relief or because I panicked and lost trust in my own body.

This time, I would like to labour with no pain relief but I'm finding it really difficult to put that trust in my own body. The thing is, I almost managed it with Olivia so I know I should be able to do it. I don't want to go into the delivery suite with the attitude that 'I can't do it', as I really feel that that will affect the outcome of the birth. How do I start to feel more positive and trust myself?
- heather_2908