Kids grow, age and change and we expect that. One of the great challenges of being a parent is adapting while still being consistent within the adaptation, just like a parent trying to be flexible within the daily schedule while still maintaining a sense of structure. It’s no different for discipline than it is for anything else and in fact, it’s probably more difficult for discipline since the heart of discipline is teaching the child and that child is going to push more and more of your buttons as she ages.
When the kids are smaller, you’re around them more and the environments are much more controlled. You can keep an eye on them and their activities and things are much more of a known quantity. You have a decent sense of the risks, hazards and temptations. They’ll still come up with new twists that catch you off-guard but if you think like a kid, you start to anticipate what can happen.
Temptations and situations develop when they enter a larger environment. More kids from other families – each family with its own values and priorities – and new surroundings mean that the parents must stretch their attention span; what new challenges can arise and what should the response be when they do?
But discipline becomes a real challenge when the kids reach the point that they’re more aware and think that they’re smarter than "the ‘rents". Rules will be questioned – sometimes rightfully – and the opportunity is now there to pursue actions and behaviors that are potentially self-destructive. Now discipline can almost reach the point of being akin to a military campaign. You have to observe and question, demand details and parse through commentary that appears straightforward to the addled teen brain but is actually short of real information. You then have to work to channel them to the options that are in their best interests and that can involve maintaining a considerable and extended period of pressure to assure their compliance. It can be unpleasant and lead to discord within the household; the child is unhappy having to comply with a semi-senile old coot and you’re unhappy too. It’s unpleasant being considered "the bad guy" and equally unpleasant enforcing accountability, especially if it means that something in which the child excels is being withheld to assure compliance.
Over the long term, it’s easy to become discouraged and doubt yourself. Expect mistakes, by both you and the child, and correct them accordingly. But remember that you’re the parent and have a much larger knowledge base as well as the responsibility to help this kid reach a productive adulthood. And then gear up for a potentially protracted campaign.