Life is full of surprises; you never know what will happen next.
When you open a box of chocolates, there is a variety of flavors available. Problem is, since they are covered in chocolate, you can't really tell what any given piece of chocolate is going to taste like. You're going to eat a chocolate (you know you are! admit it! you want chocolate!), but you won't know what you are getting until you bite into it - and then it's done. Like it or not, you've tasted it.
You never know what life is going to give you. But you live nevertheless. So every day - every new experience - is something you really don't know about until you actually live it. It may not be an experience you like. It may be the greatest experience ever. But you don't know until you've lived it, and by then it's too late to not live it.