See, I guess to me it is also important that kids learn to work hard and overcome challenges. But the idea that forcing them to work hard will teach them to work hard is sort of like the idea that forcing them to eat broccoli will teach them to like broccoli. I think if you offer broccoli regularly, and model enjoying it yourself, your kid will eventually like it. Or, if not broccoli, another healthy substitute. Whereas if you force them to eat it, they may learn to eat it, but they will never enjoy it and, worse, they will not learn to listen to what their body tells them about what to eat & when, because they've been forced to ignore that inner voice.
So I will offer DD plenty of challenging tasks, and let her decide how hard to push herself. So far (and she is only 3), she chooses to push herself. She has accomplished even more than I would have dared to try to push her into, if indeed I was that sort of parent.
That said, I think perhaps for older gifted kids who have had years of inappropriate schooling, a bit of a push might be a good thing. It is hard to overcome bad habits once they are ingrained. But I just don't think a prophylactic push is at all necessary.
