What words in the poem induce a feeling of melancholy?

Sweet day, so cool, so calm, so bright
The bridal of the earth and sky:
The dew shall weep thy fall tonight,
For thou must die.

Sweet rose, whose hue, angry and brave,
Bids the rash gazer wipe his eyes:
Thy root is ever in its grave,
And thou must die.

Sweet spring, full of sweet days and roses,
A box where sweets compacted lie:
My music shows ye have your closes,
And all must die.

Only a sweet and virtuous soul,
LIke seasoned timber, never gives;
But though the whole world turn to coal.
Then chiefly lives.