How do I encourage my daughter and point our her writing errors? I am worried about destroying my daughter's confidence, but want her to write without grammatical errors.

The other day a friend asked me how she could tell her daughter that there were many grammatical errors in her writing piece, but that the content was exactly what she was looking for.  The mom was worried she might step on her daughter's self-confidence as a writer.  This is how I approach this situation.  I would say this to the student, or to my child, without showing them the paper with my corrections on it, "You have done an excellent job in writing the content part of this paper.  Congratulations!  You grasped everything I was looking for, and I am very impressed at how you think and how you express your thoughts on paper.  Now, there are some minor errors that we need to look at and you need to fix.  If you don't fix these errors, another reader may not be able to see your great thinking process, because they will be stuck trying to figure out what you're trying to write."  I would then take out the essay, which would have my corrections on it.  During the first part of my talking, I would try to smile and physically show approval so the child feels honored....With analytical writing from ages 11 or 12 and older, I prefer correcting all grammatical and spelling errors, and making the student rewrite the piece so in the end, the student has a perfect paper.  But, if possible, I try to have the student do most of the work.