How do you tell one or both of your parents that they have failed you?

So we all have issues that are a result of our childhood… our environment growing up. It shaped who we are and how we form relationships and relate to others as adults. We are all a product of our environment and though me must hold ourselves accountable for our actions and behaviors… there are some inherent characteristics in us that we must work on to overcome. Have you ever had to to tell your parents they failed you in some way? How did you do it? What was the outcome?!?