thoreau quote

[Dean706@aol.com]

I am unable to source the following quote attributed by EB White to Thoreau 
but not further identified:
All that a man has to say or do that can possibly concern [mankind is] in 
some shape or other to tell the story of his love -- to sing; and if he is 
fortunate and keeps alive, he will be forever in love
Can anyone source this>
Many thanks,
Dean Niles