1. Fly Or Die is just another way of saying that you're going to try your hardest or (supposedly) die trying on something, such as passing a school test or getting a date with the girl you've always wanted.
2. Also used as a way to describe someone taking something too seriously.
1. "I'm going to Fly or Die at winning the lottery."
2. "That Tony kid is so Fly or Die at acing his tests. He needs to relax."