I hope that more than anything else, we want our kids to grow up to become happy, well-adjusted adults. They will have lives in reasonable balance with family, career, friends, hobbies and interests, etc. They will have enough self discipline to work towards meaningful, long term goals. But, they won't be so driven as to neglect relationships, leisure, and other forms of self care.
To help them accomplish this, their lives in childhood and adolescence need to reflect this same balance. I recommend that when it comes to school grades, the focus should be on the child's effort level much more than their actual, academic grades. I am less worried about the student who works hard for a 'C' than the lazy, gifted student who gets a 'B' on little or no effort. I will often ask kids what their 'effort GPA' would be if one were awarded. An 'effort GPA' of Bs in school seems to be the way to get a healthy balance in life. Kids who are are driven to put in a maximum effort at school (an effort GPA of 4.0) often do so as the cost of leisure, fun, relaxation, building relationships and caring for oneself. They usually end up with higher anxiety, stress, sleep problems, and overall happiness is diminished. And, they are setting the stage to do the same thing in adulthood.
However, kids whose 'effort GPA" drifts down to the 2.0 range and below will lack the self discipline to achieve meaningful long term goals in life. The doors of opportunity that will be left open for them will be beneath their ability level. The end result will likely be boredom, diminished self esteem, and a loss of vitality.
Granted, it is hard for any of us to achieve a healthy balance in life and keep it there. But, it helps to at least have some model in mind of what the balance should look like.