Why do woman get disappointed in themselves or others when their birth experience is not what they expected?

i'm on modified bed rest and bored and I figured i'd ask a burning question i've had for a while now. I've always been the laissez-faire type ( go with the flow). I didn't spend much time doing up a birth plan for my first baby as I knew that i didn't know what would happen and I would make my decisions as I went. That coupled with my trust in the fact that Medical personnel have experience and training that I don't, I figured I could trust their opinions and if needed voice my concerns. Anyways, I figure the end goal is the same for all moms, to have a healthy baby and I guess I wondered why some woman have such intense feelings about birth. This post isn't meant to belittle anyone that has those feelings just so you all know.