Some good 18th birthday sayings are, "You're just a 10-year-old with eight years of experience," "Wishing you a very warm welcome to adulthood" and "You're an adult now, that means responsibilities, don't screw it up." These sayings can make the 18-year-old laugh and think about the future.
Typically, 18th birthday sayings are meant to be unique, funny and inspirational. Birthday sayings are a tradition, and they let the person being celebrated know that he is appreciated. The 18th birthday is a milestone for a young person. In many countries and cultures, the 18th birthday marks the trip from childhood to adulthood.