This means that what works well for some kids will fail terribly for others. Half of parenting is trying out a bunch of different things to find out what works well for your kids, and is also acceptable for you. This variance is also a big reason why there is no "one true way" of raising kids, and why you shouldn't take parenting authorities too seriously.
It's also helpful to know when comparing yourself and your kids to other couples with kids. The worst is parents of a single kid with an easy disposition. They can sometimes be judgy and wonder why you don't just do what they did, because clearly they are amazing parents, and you are failing hard.