Here's why:
* Oysters: Oysters are known for containing pearls, which are valuable and rare.
* Opening an oyster: The process of opening an oyster is uncertain - you never know what you'll find inside. It's a metaphor for the unknown and the potential for great things.
* The world: This represents the vastness of possibilities and choices available in life.
In essence, the phrase implies that you have the potential to achieve great things, but you have to be willing to take risks and explore the unknown. It encourages you to pursue your dreams and seize every opportunity that comes your way.