<< I find this to be another under-discussed challenging of parenting: you can never even entertain the idea that "maybe this wasn't what I wanted"

You can absolutely think it as long as it stops there. There is a reason. At that point in the game, your needs and wants are supposed to be subordinate to those of the kids' long term survival. I could maybe understand this sentiment, oh 50 years ago, when you maybe could plausibly claim you had no idea that child rearing is not exactly easy, but unless a person is almost completely detached from society, it is near impossible to miss the "pregnancy will ruin your life" propaganda.

Consequences. They exist. Some are life altering and expected to last a long time.