This letter expresses love and gratitude for the recipient, remembering how they came into the author's life and changed it for the better. The author recalls how meeting the recipient gave them hope and happiness, filling an emptiness in their heart and making them feel alright each day with the recipient by their side. They are thankful for how the recipient brought sunshine into their life and relieved their worries, and want to express that finding someone like the recipient to love is rare.