Hi, jmh. 
My corrections are in green.
Could you help me to understand A Psalm of life by Longfellow?
Firstly, what is a good translation of "are beating funeral marches to the grave"?
And our hearts , through stout and brave,
Still, like muffled drums, are beating
Funeral marches to the grave.
Secondly, in the last stanza, I wonder what "with a heart" means here. Some translate a heart as courage, but courage cannot be a countable noun.
Let us then be up and doing
With a heart for any fate:
Still achieving, still pursuing,
Learn to labor and to wait.
Thank you in advance.