"I don't wanna grow up"

I'm not really focused enough to write anything good tonight. I've got my mind on other things. Tomorrow I have to write a note to my younger brother for his senior yearbook ad. I'm still puzzled at what to write. Do I tell him how proud I am of him, and how much I love him? Do I keep it lighthearted and write one of our many inside jokes? Do I tell him how much I'm going to miss him when he leaves? I don't know and I don't really want to think about it. I feel like once I write it he will have permission to grow up and leave, and I am pretty much dreading the day that he does leave. I feel like I have so many things to say to him, but I don't have the words to say it. What do you even write to someone who means so much to you? Well I am going to bed. Maybe the words will come to me in the morning.