My kids have grown and have kids of their own, so I have a slightly longer view than many posting here. Surprisingly, they all turned out fine. As parents we forget that there's lots of middle ground between 'my way or the highway' and 'do whatever you want.'
In my experience, there are times when it's really important to stand your ground. These are the times when your kid is toe to toe with you and asking 'who is in charge here?' This starts at about two and continues until 18. The trick is recognizing when your authority as a parent is being tested. Those are the times you have to show that you are the parent. You stand tough on the rules, ground them. Take the router or cell phone away.
But most of the time, it does not have to be a power struggle. A 10 pm internet curfew is reasonable, but perhaps on weekends, when her friend was over, they could have been more flexible with the time. As a parent, you actually have very little control over a teenager but they often control themselves if you have allowed them to make reasonable decisions as they grew up.
I tried to give my kids more responsibility for their choices as they got older and I considered 17 to be a pivotal year. By then, they were allowed to make many of their own decisions, and suffer the cosequenses. (Staying up late == a bad day at school). Remember, your job is to raise responsible adults, not perfect children.