End with, I love you.
Every letter he wrote.
The summary might express his feeling of depth.
Why?
He refuses to love anyone else.

He stated greatly of her support.
That without it he be drowning in nothing but trouble.
He pointed to her being his life support.

For she has saved him in his worst time.
So yes, she a diamond within his eyes.
Which is why?
All his letters ended with I love you.