Analysis of Oh, my belovèd, have you thought of this

Oh, my belovèd, have you thought of this:
How in the years to come unscrupulous Time,
More cruel than Death, will tear you from my kiss,
And make you old, and leave me in my prime?
How you and I, who scale together yet
A little while the sweet, immortal height
No pilgrim may remember or forget,
As sure as the world turns, some granite night
Shall lie awake and know the gracious flame
Gone out forever on the mutual stone;
And call to mind that on the day you came
I was a child, and you a hero grown ?
And the night pass, and the strange morning break
Upon our anguish for each other's sake !