I think one of the central realizations required to be an adult, at least it has been for me, is that fault matters almost not at all. Responsibility and fault are almost entirely decoupled. If something is a way and you want it to be another way, there is often no one else that will make it that other way except you.
When younger, I felt a deep injustice had been done to me if I was being held responsible for something that wasn't my fault. But now I see that this is sort of the whole idea of responsibility: You're on the hook, no matter whose fault it is. And that sort of sucks, but it's also sorta zen once you get it.