We learn by failure, coddling a child within it's abilities is anethema to creating independent, curious, creative people, that can challenge themselves and know thier limits.
.... ugh, I feel a blog post or some poetic vitriol coming on.
Failure isn't necessarily a bad thing. And the willingness to fail and learn from your failures is an incredibly powerful thing.
Ask anyone who regularly teaches both adults and children (musical instrument instructors, foreign language instructors, etc) and they'll tell you that one of the main thing that separates their adult students from their child students is that the children learn much faster because initial failure doesn't bother them. Adult students are paralyzingly frightened of failing, and this significantly impedes their progress in learning new skills. But children seem to understand and be more comfortable with the reality that failure is part of the learning process. You can't learn to play piano (as an example) without first playing the piano very, very ,very badly. :-)
BTW, I think this is why the currently popular advice to "fail early and often" is good advice. Yes, success is better than failure, but the fear of failure and the unwillingness to accept the possibility of failure can be crippling, and IMHO is a major differentiation between those people who do eventually succeed at great things, and the vast majority of us who just dream of doing great things.
Failure is necessary to success. You learn more from it, and it teaches patience. I'm glad I was allowed to fail a lot as child, I credit it with making me who I am today.
The point is not about failing or succeeding, it's about having a mindset that allows you to make efforts and improve, rather than believe that you can't change things and just give up.
Surely the answer is to think short-term, and keep aiming a little higher than your previous best. I'm not sure children are very good at thinking long-term, anyway.
.... ugh, I feel a blog post or some poetic vitriol coming on.