It's not about the fact that the kid failed and that the kid cried it's about the fact that the father instilled the wrong *type* of belief in him.

The best example I can think of comes from a book called Good to Great by Jim Collins.
They called an idea on positive thinking 'The Stockdale Paradox'.

Basically it means that you never waver in your belief that one day you will achieve your goal but you face the brutal reality of your situation. In this case the kid should have practised more because he wasn't good enough. That was his brutal reality. Had he really wanted it and had the belief instilled that 'one day' he would win, if he kept practising, kept working, concentrating and focusing then sooner or later he would prevail and beat the opposition.

Stockdale was a prisoner of war who survived years of torture and brutality. When asked who didn't make it, he replied 'That's easy, the optimists'. He never wavered in the belief that one day he'd go home, he just never (like the optimist) expected it by Christmas, or Easter or next year. The optimistic people did and died of a broken heart.

Positive thinking is good. It's just it has to be the right type of positive thinking.