I also had a positive mindset about giving birth, I would say I was more curious about what it would be like than scared! Two births later and I still have a positive mindset about giving birth and (if practical circumstances aligned) would happily have a third baby with no worries.
Like you, I have a high pain threshold (I have endometriosis to thank for that) and I feel that was probably a benefit in my case, but of course 'high pain threshold' (and giving birth) varies from person to person.
I remember posting on here pre-birth asking about hypnobirthing and saying that I was intending to have as relaxing a labour as possible. I was laughed at by many posters, but I'm glad my mindset wasn't shaken because I did have relaxing, chilled out labours with both of my babies (albeit they were slightly longer in duration than I would have liked, but I dealt with it)!
I gave birth to both of my babies in water (if you like a bath/jacuzzi/swimming, chances are you'll love the relief that water gives you, it takes the weight off and the warmth is soothing), used hypnobirthing techniques (highly recommend) and some gas and air towards the end (also recommend - if you decide that you don't like/need it it's easy to put down).
A couple of posters have likened giving birth to running a marathon and I'd agree with that. It's not exactly easy and it's certainly a workout, but the achievement that you feel at the end is unlike no other. If you prepare beforehand by equipping yourself with tools such as knowledge about the process, a positive fear free mindset and ways in which to cope (breathing techniques, warm bath/pool, massage, etc.) that's the equivalent of your marathon training.
If you haven't yet explored it, I recommend looking into doing a hypnobirthing course. It sounds 'hippy dippy' (or at least it did to me!), but it's science based and many NHS hospitals offer ante natal courses (mine did). I felt I learnt more about the process of giving birth than I did during standard ante natal classs (it was good to be able to recognise exactly what my body was doing and why, plus know how best to deal with it/what my options were) and the breathing and relaxation techniques were invaluable.