Question: What is the more effective incentive in shaping a young boys life? Being shown a Negative result or a Positive result?

Example I: An "Old Man" who is bitter, and beaten down by life sees a young boy who is happy and full of energy. The boy is whistling to himself, and is not shy about doing so in the presence of the Old Man. Looking down at the boy, he cracks a small smile as he remembers his youth and says, "Don't ever lose your youthful attitude or you will become a bitter old man like me!" The little boy recoils away from the old man in revulsion.
Example II: The same boy, still whistling out loud is spotted by another man who is the same age as the first one, but is healthy and successful in his life. This other man sees the boy and whistles along with the child! Looking down at the boy he says, "Don't ever lose your youthful attitude and you will become a successful man like me!" The little boy starts whistling again, and is again joined in by the older man.

So, back to the question. Is the revulsion at seeing the bitter old man more or less powerful to the boy then the positive experience of whistling with the successful man? Which will be more of a guiding life experience for the child to look back on? Will he say to himself: I DON'T want to be like the bitter old man, so I will always keep my youthful attitude!" Or, does he say to himself: "I want to be JUST like the successful man when I am old, so I will always keep my youthful attitude!"