My own Mom was barely 21 when she had me and she parented from "the do it the opposite way" of your own parents. I was almost 36 when I had my first child and I definitely tried to do it from the make your own choices but would default into the opposite zone as well.
The default would be most noticeable when my children's had strong reactions to my parenting decisions. How do we stop defaulting and start making our own thoughtful choices? One important way is to take a step back and remember what it was that our parents used to do in a similar situation.And then ask, is this something that we want to continue doing or do we want to do it a different way?
For example, I was very strict with our children's diet. I had the limited sugar ( used to call it white death) and no fast foods rule when my children were young. My children and their spouses get to decide what they want to do with their children's diet. There were definitely some positive and negative consequences to that rule. Let the decision be a conscious one and no longer the fault of our parents.