Of course, start with ' Dear (enter your name),'
Then continue with saying what year it is, explain your thoughts at the moment, tell him/her what you are doing and interested in. Think about all your positive and negative sides of you at the moment and write them down. Tell him/her what you expect to do in the future and how you see yourself when you are 45 years old. Tell yourself what traits in your personality you should change, and what you wish stays the same. One thing that always works with professors is to write that you want to keep the child in you alive and that you should never forget to have fun.
Good luck, hope I helped :)
