My grandfather, who I never met, has part of a poem by A.E. Housman on his tombstone. It says just about everything there is to say when you really get down to it:
Into my heart an air that kills
From yon far country blows:
What are those blue remembered hills,
What spires, what farms are those?
That is the land of lost content,
I see it shining plain,
The happy highways where I went
And cannot come again.