To preserve yourself as the center of the world, to stay your own best authority on everything, your own expert on all topics, infallible, omniscient. Always, every time of the month, forever: Use birth control
A birthday is the day that you were born, and it indicates how old you are and how long you have been in this world. Each birthday will mark the fact that you are a year older, and often a celebration is held to honor this fact. Sometimes a birthday is not a welcome event, especially as you age, and there are men and women both who lie about their age and change the year of their birth in order to seem younger than they really are.