"Hey [Friend's Name],
On this special day, I just wanted to take a moment to appreciate and celebrate our friendship. You bring so much joy, love, and light into my life, and I'm honored to have you by my side.
I'm grateful for our late-night conversations, silly jokes, and deep talks. I'm thankful for the adventures we've had, the memories we've created, and the dreams we're still working on.
You're more than just a friend to me; you're a confidant, a partner in crime, and a constant source of support. I promise to always be there for you, through thick and thin.
So here's to us, and to many more years of friendship, laughter, and making more unforgettable memories together!
Happy Friendship Day, my dear friend!
With love and appreciation,
[Your Name]"
Feel free to customize it to fit your personal style and friendship!