Oh, that's a tough one. Friends are special, and you want to make sure your message really conveys how much they mean to you. I'd suggest starting with a warm greeting, something like "Dear Friend, wishing you a season of joy and happiness." Then, take a moment to think about what makes this person so special to you. Maybe it's their kindness or their humor or their support during difficult times. Whatever it is, try to express it in a few heartfelt sentences. Finally, end with a simple "I'm so grateful to have you in my life."