The things you are describing - developing long-term goals, goal-directed hard work, calculated (but not impulsive) risk-taking, are manifestations of high executive functioning, which is an even better predictor of success than IQ, according to an article Bostonian recently posted here.

Fortunately, executive functioning can be developed and trained; unfortunately,one of the things that develops it is practice with progressively more difficult tasks requiring planning, problem-solving, and goal-directed hard work. So one of the very real costs of under-challenge for gifted children is a lack of opportunity to develop skills in executive functioning.