Spiritually, how does one recognize the difference between a 'sign' and a 'test'? For example; If a boy really wanted to play guitar in a rock 'n roll band and he had a car accident which paralyzed his right leg, would this be a sign telling him to focus his efforts elsewhere or a test of his determination to succeed?

(This was a real dilemma for me about 8 years ago when I was asked to appear as an expert witness against a boy who was in this situation)