While it is important to maintain your boundaries and to protect yourself when you are having conflict with your teen, it is more important to keep perspective. What I mean by keep perspective is remember the parent you want to be in spite of their insane behavior, don’t make the issues more important than they really are, and don’t take their behavior personally.
You are the parent and even though at times your teenager seems to have adult like moments remember that their frontal lobe has not fully connected. They have not yet had enough failure and successes to have their own healthy perspective. Your relationship is often unfair and can be a one-way street. Remember that your job is to maintain the relationship while setting boundaries and planting seeds. They are not equipped yet to take care of you emotionally and your teen is in essence battling for independence from you while not being able to function without you. Be patient with this battle and love them unconditionally through it.