This is one of those brain benders that I don't think anyone can answer with any certainty. I don't know of anyone who would consider themselves a successful parent. A person, willfully or not, is charged with being responsible for a human life. And although some people do better than others with this responsibility, I don't think anyone would truthfully claim that they did a great job.
Jan's pregnancy was planned, and she did tons of research prior to the delivery on what and what not to do. But, as prepared as she/we thought we were, there was still that moment when we brought Sean home from the hospital. We put him in a blanket lined laundry basket on the living room floor, because that seemed like the thing to do. As we were looking down at him, we said, almost at the same time ... "What do we do now?"
And no matter how or why the planned milestones, markers and expectations changed over the years, I think our guiding principle always stayed the same. We just wanted to do a better job than we perceived our parents doing with us. And if and when Sean has children of his own, we'd expect him to do the same thing.
You just do the best job you can, and hope it turns out okay.