Women's bodies don't need extra pushes, BUT... they can be stalled and upset easily by an abrupt change in environment, fear, anxiety or being threatened (if you don't go into labour by X date, I'll induce you!!).
Adrenaline knocks out things like oxytocin and endorphins, but the solution isn't to push your body harder, but rather to respect it. If you don't feel safe, your body may try to stall your labour - after all, how safe would it have been if our ancient selves would give birth in the midst of a life-threatening fight? Instead our bodies wait.
Emotional issues can also cause you to unintentionally "hang onto" the baby. Fear of birth, etc. Any of these things could lead to a longer or harder labour than was necessary.
My first labour, with my daughter, was 44 hours.
I know, without a doubt, that I did this to myself. It did not need to be 44 hours of hard labour. Firstly: I was too nervous about throwing up and actually refused to eat! A car with no gas can't get anywhere.
Then, because hard labour hit in the evening, I'd gone almost 18 hours with no sleep BEFORE labour started... and then did not sleep for the next 44 hours. Sleep is necessary for your body to function. I didn't sleep when I could have (in early, piddly labour) because I was too excited. I really could have used someone to tell me, "Relax! It's just birth!". Just because I have a few real contractions doesn't mean the exciting part of the show is happening right now.
I also pushed my daughter to come out. Not by medical induction, but with my thoughts and my actions. She's VERY stubborn, and very contrary - she hates being told what to do and I'm sure she didn't appreciate my constant hounding to her to come out, come out!
I became very obsessed with my due date the first time, and when it went flying by... well, I wasn't happy about that. Every day I woke up disappointed I wasn't in labour, and every night I woke up praying I would go into labour. This was a really unhealthy way to think!
The next two times I got pregnant I decided: NO MORE DUE DATES! I boycotted them. I frequently forget how many "weeks" I am, I don't keep track, I don't think about it, I don't tell *anyone* (not even my husband) my 'due date' and instead have a due 'area'.
I'll deliver sometime in the fall, when my baby is totally ready and not one minute before!!
Another mantra that really helped me during the whole prodromal labour and endless labour feeling was this: every contraction I'm having is bringing my body closer to birth. Every contraction is needed, wanted, loved - because it brings me closer to my baby. No contractions are 'pointless'; even the smallest step gets me closer to the finish line.
There is no such thing as taking a step backwards in birth!