I think it's also to try and remember that many many 2nd labors/deliveries are far shorter than the first ones. It might be easier to stick it out and hold your ground if you keep reminding yourself that it probably won't take as long as the first one did.
Here's my labor/pushing times... the difference is very dramatic.
DS - 27 hours of labor with 4 hours of pushing - had an epidural and have always believed that is why I had to push for so long. If you can't feel the muscles, it's far harder to push.
DD - 4 hours of labor with 2 contractions that pushed baby out (I did not actively push, my body just did it). No pain meds, no epidural. 13 minutes from 4cm to baby delivered.
Yes, when I was checked and told I was 4cm, I did ask for an epidural, but if I had realized or remembered how much faster things could have gone, I don't think I would have even asked. As it turned out (happily!), as soon as the anesthesiologist walked into the room, I felt the urge to push and out came DD!
It also helped that my nurses were very supportive and had told me that their 2nd births were too fast for anything but natural, as well. This was at a large Kaiser hospital, so I was surprised to find them so supportive.
With #2, I was feeling transition before I got to 4cm, so I was a bit confused. I tried telling myself that it didn't matter what the cms were, what mattered was how I felt. Kept reminding myself that I could make it through 1 minute at a time. Always picking a small point to focus on as a contraction started (not necessarily anything special or even the same thing for each contrax).
Oh, and as a PP said, positioning can make a world of difference. DS was postier, but DD was in a perfect birthing position for quite a while before labor. Spinningbabies.com has lots of info on getting and keeping babies in good position.
