请根据以下提示，结合事例，就梦想这一话题，用英语写一篇短文。
Everyone has their dreams. Fifteen years old is an age when teenagers have beautiful dreams. What’s your dream and what caused you to have this dream?
注意：①无须写标题；
②除诗歌外，文体不限；
③文中不得透露个人姓名和学校名称；
④词数不少于120，如引用提示语则不计入总词数。