My Five Cents

Ollie's granny tells him if he uses his five cents wisely, he will be very, very happy. Ollie wants to be happy, and his granny is very smart, so he makes a plan. He takes his five cents to Mr. Rubin's candy store and buys five candies for one cent each. Then he goes to school, and during playtime, he sells the candies for two cents each. Now he has ten cents instead of five. He has used his five cents wisely. The next day, Ollie uses the money he made to buy ten more candies for one cent each and sells them for two cents each. He makes more and more money every day. And every day he buys more candies and has to work harder to sell them. He doesn't have any time to play and have fun. Ollie is not very happy. In fact, Ollie is very unhappy. But Granny is very smart, so Ollie keeps doing it.
Why has Granny told Ollie that using his five cents wisely would make him very, very happy? Ollie is doing what she said he should do, but he is not happy. Is it possible Granny could be wrong?
Will Ollie ever be happy?