Actually, Bocci, I thought this type of phrase was called a Chiasmus, though parallelism is certainly appropriate too.

Kennedy followed in Churchill's literary tradition, where Churchill's chiasmi helped inspire a nation throughout WWII. His quotes are available everywhere so there's no point reciting them here.

Time for an on-topic chiasmus,

It's bound to be fun, and it's fun to be bound!

and something from one of my heroes, Kermit the Frog.

Time's fun when you're having flies!