It is living the wild man or wild woman in you. It is letting go of the fears and inhibitions of the unknown and feeling the freedom to explore new adventures. It is the feeling of riding a roller coaster for the very first time.
While the car is slowly pulling up that first hill, your heart is pounding, knowing you are going to plunge down the other side at any moment. You know you won't get hurt, but you are scared anyway. When you finally go over the top and head downward, you may laugh and scream but you feel the exhilaration and excitement of a new sensation. It took courage but retrospectively, you think it was fun. That is truly the heart of courageous exploration.