How does nature prepare us for ultimate rest in "Thanatopsis"?

In this excellent poem, which is famous for its expression
of Romanticism and an organic, cyclical view of nature, Nature is shown as a force that
is ultimately benevolent and with whom we can have a relationship whilst alive. Note the
way in which we are shown that we can be comforted by Nature when we are depressed by
thoughts of our ultimate death:

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When thoughts

Of
the last bitter hour come like a blight

Over thy spirit,
and sad images

Of the stern agony, and shroud, and
pall,

And breathless darkness, and the narrow
house,

Make thee to shudder, and grow sick at
heart;--

Go forth, under the open sky, and
list

To Nature's teachings, while from all
around--

Earth and her waters, and the depths of
air--

Comes a still
voice...

The images used in
these lines all are common images refering to death: from the pain of a fatal illness to
enclosure and burial in a coffin. However, in spite of the grim death-imagery that the
opening stanza contains, it is clear that Nature wants to communicate with us, consoling
us about our fate, reassuring us that death is not as we think of it; rather it is only
a re-joining of ourselves to Nature, which gave us life in the first
place.