Marshall Clarke, from Plymouth, died peacefully on October 29 next to his mother, Lara, and grandmother, Elsie, after spending three years battling against Late Infantile Batten Disease.
The youngster had been bed-ridden for ten months and lost his vision, mobility and ability to communicate.
But before he died, he managed to write one last letter to his friends and his family have now decided to share it, just days before his eighth birthday.
In the letter, posted on an online blog by his grandmother, Marshall described all the things he’s now able to do.
He wrote: ‘It’s okay because nana has told me all about it (heaven) and about all the wonderful things I will be able to do when I am there.
‘There will be loads of slides and strawberries and cupcakes and I will be able to eat again and run and watch videos.
‘Be happy for me that I am no longer trapped in a body that stopped me from enjoying my childhood. I am now free to do all the things I have missed so very much.’
Marshall was diagnosed with the condition, a disorder of the nervous system, in September 2013, becoming one of only 24 children in the UK to suffer from the disease.
Within 18 months of being diagnosed, Marshall lost his vision and suffered night terrors, uncontrollable seizures and tremors which meant he couldn’t feed himself.
As his condition continued to deteriorate, trained nurse Elsie, who cared for little Marshall at her home, said he would fall to the floor up to 40 times a day.
But she said he never cried, never complained and never gave up.
Elsie said: ‘He is in heaven now. This was his hell and now he is free.’
‘His determination and his happiness throughout it all has just amazed me. When he lost the ability to walk, he learnt to crawl.
‘When he struggled to feed himself using a knife and fork, he swapped his cutlery for two forks and would eat one mouthful at a time.’
Marshall’s funeral will be held on November 8, to coincide with his eighth birthday, and will be superhero-themed.