It kind of gets you right here to see the manliest men in history putting a pen to paper to express their soft side. We saw that in Teddy Roosevelt's diary entry
not long ago. On a happier subject, here's a note that Samuel Clemens (also known as Mark Twain) wrote to his wife Olivia in 1888.
Hartford, Nov. 27/88
Livy Darling, I am grateful — gratefuler than ever before — that you were born, & that your love is mine & our two lives woven & welded together!
See the full size version at Letters of Note. Link
(Image credit: The Mark Twain House & Museum