Dear [Name],
I am writing this letter to express my deepest gratitude for [specific reason]. I am truly grateful for your [kindness/support/generosity] and wanted to let you know how much it means to me.
I am truly fortunate to have someone like you in my life and I want to take this opportunity to thank you from the bottom of my heart. Your [support/love] has been a source of strength and inspiration for me.
Once again, thank you for everything you have done for me. I am truly grateful and will always cherish your [friendship/support]. I hope to have the opportunity to repay your kindness in the future.
[Your Name]