Analysis of Retrospection

I turn these leaves with thronging thoughts, and say,
Alas! how many friends of youth are dead;
How many visions of fair hope have fled,
Since first, my Muse, we met.--So speeds away
Life, and its shadows; yet we sit and sing,
Stretched in the noontide bower, as if the day
Declined not, and we yet might trill our lay
Beneath the pleasant morning's purple wing
That fans us; while aloft the gay clouds shine!
Oh, ere the coming of the long cold night,
Religion, may we bless thy purer light,
That still shall warm us, when the tints decline
O'er earth's dim hemisphere; and sad we gaze
On the vain visions of our passing days!