On the run up to birth I constantly reminded myself that my body was made to do this, and to cope with it! Pain relief is a modern invention, I reminded myself that hundreds of years ago women just did what they felt was right. I did a fair bit of meditation and visualisation to help relax me.
Basically I stayed active, went about my normal day. When the contractions were getting strong I started to hum while I had them which seemed to help me cope. When they were too intense to get up and walk about in between I straddled a dining chair and carried on for a few more hours. Midwife had advised to stay at home until I felt I NEEDED to go to to the birth centre, when I NEEDED the pool. I went in and was found to be 7cm and progressing fast, they were worried about not being able to fill the pool! I think just listening to your body is most important, if you fancy changing position for one contraction then go for it. Your body knows what it's doing and how to get the baby out, trust it! I was reclined in the pool and out of no where decided I needed to be on all fours, 2 contractions later I wanted to be reclined again. Baby had just started to crown, I really believe that that sudden urge was what brought baby down and helped her turn (she was back to back but crowned facing my back)
Accepting that it will hurt helped me too. I kept telling myself 'I know this hurts, but each one means I'm closer to meeting my baby' Also reminding myself 'no one ever died or even passed out from the pain, It's not that bad'
If you REALLY believe you can do it you can

but also fear plays a huge part I think, make sure you're not scared. apprehensive, nervous, yes but not scared iygwim?