You are working toward a time, maybe 15 or 20 years in the future, when you transition from a parent role to that of your child’s best friend. Until that time, you have parenting responsibilities. You are a model, a disciplinarian, a teacher, a guide and you are responsible for setting parameters within which the child must operate.
You are not their best buddy. And they do not exist for you to use them to figure out your own problems. You provide guidance by your example and your understanding of unselfish love. By your example, you provide ways of dealing with discomfort, hate, joy, judgment, fear, discipline, support, and how you deal with adversity. Doing this requires a parent to become aware of their own life choices and not to pass on contaminated or wrong information to the child. You model effective and necessary actions that they must understand are appropriate even if in your own life you often take other paths.
As a parent you now have the responsibility of building a foundation for another human being that is not limited by your own programming or experiences. Good parenting passes along the goodness, and all the things that will help them become beautiful beings. When parenting is no longer necessary, hopefully by mutual agreement, the friendship and deep bonds of love you have shared flow naturally.