Good question!
I think we, as parents, can provide our children with a foundation from which to build a successful life, but that's about it. What our children *do* with that foundation is ultimately up to them.
In my book, I will feel I've been successful as a parent, if my sons become productive, self-sustaining members of society. I will feel I've won the gold medal of parenting, if my sons actually *want* to come spend time with me after they've established their own households. (I don't want any "guilt trip" visits.) While I would very much love for them to feel happy, I also know that too often being happy is something we choose to be or not be. I can't force them to be happy, I can only hope they'll be happy with the life they create for themselves.
Will my sons make the same mistakes as me and my husband? I hope not. I hope they learn from our example, both negative and positive. But if they do, I hope I have the courage and fortitude as a parent to let them make their own mistakes. Mistakes are sometimes the best way to learn the necessary lessons of life.
I think "nurture" plays a big role for our children. As a teacher starting her 19th year in the classroom, I can see what poor nurturing can do to a child. But, at the same time, I also believe we're hard wired to be a certain personality. All that nurture is filtered through one's hard-wired personality and the outcome can be different than what we, as parents, hope or imagine it to be. For example, my mom saved all my elementary school report cards. From kindergarten through 6th grade (and beyond) all my teachers said I was a sunny, happy child, always smiling and eager to help. I had a rough childhood, one that wasn't always pleasant. But, my sunny, Pollyanna personality filtered all that negative stuff and I took away the silver lining. Another example, my youngest son marches to the beat of his own drummer, as it were. He's a great kid and I love him dearly, but he just processes things differently than 95% of the kids his age that I've worked with. I'm often stunned by the "message" he takes from various situations and have had to do lots of rethinking of how I handle him. (Sorry, I can't think of a good example at present.) It's made for some very interesting parenting moments.
As my kids near high school graduation, college and beyond, I'm faced with the knowledge that only too soon, I'll have to "walk my talk" and take a back seat in my sons' lives. In many ways, I look forward to relinquishing control to their good judgement. But, many times, I look at the dumb, teenage boy things they do and wonder how in the blazes I'm supposed to stand back and shut up and let them fall flat on their faces. <sigh> I have a much greater appreciation now for what my mom went through when she left me at university and watched my sister move out at 15. Oh, boy...
Hope this put off at least a round of bathroom cleaning!