Dear [name of friend],
I just wanted to thank you for being such a great friend. I've known you for years, and you've always been there for me when I needed it (and even when I didn't). You've taught me so much about myself and the world around us, and I couldn't be prouder to call you my friend.
I'm so happy that we're able to spend more time together now that you're moving back to [place]. I can't wait to see what comes next for us!
Thank you for your friendship. It is a source of joy and happiness for me.
I have learned so much from you, and I am grateful for the ways you have helped me grow as a person. I am looking forward to spending more time with you in the future.
Thank you so much for being such a great friend. You have impacted my life in so many positive ways and it's been an honor to share so many laughs with you. I can't wait to spend more time with you in the future!