What is the sentence about Colin's autism written in the secret garden?

The autistic sentence written by Colin in The Secret Garden is a depressed little boy whose experience is unfortunate. His mother died as soon as he was born. Father couldn't bear the blow and was disheartened from then on. He traveled abroad all the year round and almost forgot him. He thinks that breathing fresh air can kill him, but if he thinks about it carefully, nothing can kill him. This book is an ode to nature and gardening, and it is also a pure and passionate pastoral. It is not a fairy tale, but it has the characteristics of pure fairy tale symbol.