"Be not afraid of greatness: Some are born great, some achieve greatness,

 and some have greatness thrust upon them." William Shakespeare

 We should not be afraid of greatness in any way. Greatness is a positive

 thing. "Some are born into greatness" means some people are born into

 families who are known for their greatness: Some of the royal families,

 children of Kings, Queens etc.. Here in the U.S., the Kennedy family for

 example. "Some achieve greatness" means some people contribute the 

 world with inventions, being a wonderful leader, athletes, entertainers, 

 a famous director like Steven Spielberg are examples of those who achieve

 greatness.

"And some have greatness thrust upon them" means greatness comes to 

 them for something they had done by accident or without wanting the 

 greatness.