This letter has struck me every time I come across it. Probably the most unpleasant duty short of fighting against Scott...

Arlington, Washington City P.O.
April 20, 1861
General:

Since my interview with you on the 18th instant I have felt that I ought not longer to retain my commission in the Army. I therefore tender my resignation, which I request you will recommend for acceptance.

It would have been presented at once, but for the struggle it has cost me to separate myself from a service to which I have devoted all the best years of my life & all the ability I possessed.

During the whole of that time, more than 30 years, I have experienced nothing but kindness from my superiors, & the most cordial friendship from my companions. To no one Genl have I been as much indebted as to yourself for uniform kindness & consideration, & it has always been my ardent desire to merit your approbation.

I shall carry with me to the grave the most grateful recollections of your kind consideration, & your name & fame will always be dear to me. Save in the defense of my native State, I never desire again to draw my sword.

Be pleased to accept my most earnest wishes for the continuance of your happiness & prosperity & believe me most truly yours

R. E. Lee

http://www.sonofthesouth.net/leefoundation/LettersWinfiedScott.htm