It's the handwritten note. How after all these years I can still hear her voice when I read it.
It's the realization and then the letting go of ever being able to photograph or say or write or sing or do some sort of expressive dance which could somehow convey how grateful you are for those people whose very existence was and will always be a gift.
A simple thank you is never enough. They are one of the reasons you live your life this way.