It was August 2017, just a few days after Addison Yandle had started the fourth grade, when her parents noticed that something seemed off. "She was more reserved than normal, and she was anxious about going to school," her father, Dr Chris Yandle, tells PEOPLE. "We'd later learn that she was being bullied by a supposed friend of hers." Wanting to do something to ease her anxiety, Chris decided to write Addison a lunch note, which read, "Be nice to others. Not everyone will look like you. Learn to spot the unique and special things in other people. You have the power to change someone's life!" "In my mind, I thought having a note from dad scribbled on her sandwich bag might make her smile or brighten her day," he explains of the note. "To me, it was my way of saying 'I'm here,' without actually sitting next to her at lunch." But what Chris didn't know then was that his notes would take on a life of their own. Since that day, the father of two has continued to write Addison daily notes with inspirational sayings and quotes. He has written a total of 691 notes and in 2018 published a book on them called Lucky Enough. Today, as Addison prepares to enter the 8th grade, Chris hopes he will continue to be the father his children need and that his teen daughter will grow into "a strong, confident woman."