Physiological birth is unpredictable. No matter where someone sits on the spectrum between birth being a natural, normal part of life and something that is inherently dangerous and needs to be monitored and managed closely, most people will concede that you cannot wholly predict how it will unfold.
People's opinions (on anything and everything) stem from a combination of their education, beliefs, wider worldview and own lived experience. Unless you make a conscious effort to see things from other people's points of view and to acknowledge that what might be right for you won't necessarily be right for someone else, it can lead to very heated discussions, putting it mildly.
With this in mind, some people believe that because you can't predict with complete accuracy how a birth will go, there is no point in preparing for birth, or for putting together a birth plan. It'll go how it'll go and you're fooling yourself if you believe you can control it. That this leads to unrealistic expectations and ultimately, to disappointment.
While I agree that you cannot control how birth progresses, I do believe that you can influence it. That you can prepare yourself mentally, emotionally and physically to give yourself the best chance of coming through the crucible of birth stronger and more confident than you were before. That you can understand the process of birth and how controlling your environment can give your body the best chance to release the necessary hormones for the process to unfold smoothly. That you can understand how important the subconscious beliefs we all hold about birth (which is itself an unconscious process) are and how these can influence a birth's progress. And also, that you can think about the things that are most important to you in the event of your baby's birth, so that if events take an unexpected turn, you can still own what's happening and feel fully part of the process.
More practical ideas for ways to achieve this will become the subjects of future posts. What helped you to prepare for birthing? What helped your partner or other support prepare? What, in retrospect, do you wish you'd known in advance?