I had a bad time first time round. Long labour, 2 days, 8hrs of pushing, bluelight transfer, lots of intervention, emcs.
I ended up with ptsd and pnd and couldn't contemplate having another for years. I felt all sorts of things, guilt, anger, disappointment, resentment, loss and it caused flashbacks and panic attacks and I swore I'd never do it again. I did do it again because I appear to have two children. 
The most important thing I can tell you is that the way to have a positive birth is not to pin your hopes on certain outcomes. When I was pregnant for the second time, I obsessively read stories of easier 2nd deliveries, shorter deliveries, uncomplicated 2nd deliveries and I realised quite quickly that they wouldn't actually help if I had another complicated delivery. What if it was longer? More difficult? I realised that what I had to do was work out why I was traumatised and try and stop that happening again.
When I was pregnant first time round, I had this notion of having a home water birth, it was going to be a lovely, positive and bonding experience. What actually happened that I had an intervention heavy, painful experience and the trauma came from the loss of control. I just hadn't contemplated that it could be so far from my expectations and in the end I just felt like the labour was happening to me, like something was being done to my unwilling and hurt body and I had to endure it. Plus, the pain was excruciating and I couldn't control my breathing, let alone my reactions to everything that was happening.
I realised that instead of hoping for a perfect birth, or even a better birth than first time round, I would remove a lot of the anxiety by having a better and more informed approach. I managed this a couple of ways. I had a debrief to understand better what happened first time round. That way I could stop feeling guilty and blaming myself because what I found out was that my dd was unbirthable due to her position. I could not have prevented that. I also made myself consider how I would handle things next time. So say that the same thing happened again, instead of lying there terrified and helpless, what choices could or would I make? You can't control what happens during a delivery but you can exercise control over the variables. So if you were induced last time and that happens again, instead of entering it with panic and fear, what parts of it would you do differently? If pain was an issue, what pain relief will you consider and when will you consider it. Would you consider an elcs instead? Who will you have with you when giving birth? Would a doula help? Support is very important.
You also have to forgive yourself. Don't ever believe that your experiences first time round, during labour or afterwards were your fault or deserved. You aren't a wimp, pain thresholds are irrelevant, you didn't fail yourself, your baby or anybody else. You were traumatised and that has a ripple effect.
I had my 2nd child 20 months ago and labour was a carbon copy of first time round. Only longer. BUT... I went into theatre laughing and I came out laughing. It was such a positive experience. I look back with a smile, not a grimace. And first time round I had the back to back contractions, no break, no let up, constant, crippling pain. I thought I would die. Second time round, it didn't hurt a bit. Not a smidge of pain. I can't tell you why that happened but I know that before I went into labour I KNEW that if it was as bad as last time, I would NOT be doing it on gas and air alone. Not being in crippling pain for hours was a revelation. I don't believe that any woman should have to endure such terrible pain for so long. You don't get a medal at the end of it. Only a baby. And you have to care for that baby. You deserve to do it without the weight of PND round your neck.
Can I also say, that I was shocked by having ds in another way. After having dd, I felt so altered. I was anxious all the time. I was frightened I would never feel like me again. Not laugh or cry spontaneously or enjoy anything. The world contracted down to this black hole of anxiety and only the baby. I couldn't believe I'd ever feel normal. After ds, I felt like me. No more no less. Nothing was different. I just had another baby. I was floored by this revelation. I assumed that having a baby would always be something which rocked the foundations of my existence. Nope, it was just a positive experience and our family growing. Of course it was exhausting and difficult at times, I think it has to be, but I was never anything other than me iyswim.
They do have dedicated midwives who help with birth trauma and our local hospital has a chap who does birth trauma therapy. There is help out there. Avail yourself of it.
Having ds is the best and most healing thing I've ever done.