If a person never felt any frustration during his childhood, he will be easily defeated and feel frustrated after growing up. Learning how to handle with frustration is a good lesson for a child. A "bad" feeling is part of a human's feeling. One needs to feel it and learn from it.
If one belive a child without hard training can be sucessful in the society, I sinerely disagree. On average, a child will be most likely to be an average child, if he receives average training. What is the average family income for the US, $40,000? (i am not sure.). I do want my child and his child to have a better life than that. I do not belive our chinese children to be smarter, on average, than any other children of any race. No pain no gain. The happy childhood of child has is earned by his parents, like you. But if he does not work hard, he will be an average person with an averagre life level. Of course nothing is wrong with that as long as one feels OK about his children/grandchildren. Of course if you have a genius child, it is different. On avearage, our children are average children.
Enjoying life does not necessarily directly conflict with enjoying working. I guess some of us has never got the feeling of "enjoying working".
Pushing too hard is obviously bad; no doubt. In my eye, no-pushing is just as bad as pushing too hard. Without any pushing, i do not think the children will be 心理健康. Look at those super rich family, their children do not need to worry anything. Do you really like the life style of some of them?