Goliath was a giant of a man. He struck fear in everyone's heart. One day David asked his brother " why don't you stand up and fight the giant"? The brothers replied " Don't you see he is too big to hit". But David said" He is not too big to hit, he is too big to miss. The rest is history. David killed the giant with the slingshot. Same giant different perception.
To a positive thinker attitude can be a stepping stone to success. To a negative thinker it can be a stumbling block.