One of the most surprising things about being a parent is the amount you have to improvise. Way more than in anything else I've done, despite this being probably the most commonly done thing I've done. I think it's because kids are incomparable generators of chaos.
Is this really surprising? Kids are a moving target; both their ambitions and their abilities change at a pace unknown to adults. The accumulated wisdom and experience of parents past has value, but only as a source of rules of thumb. Kids are high variance, and details matter.