The two major themes of "The Going," by Thomas Hardy, are departure and yearning.
Departure is shown in the title; the poem concerns a woman who has "gone," or left, without explanation or warning. The first line of the poem, "Why did you give no hint that night," shows that the departure was not predictable, but sudden and surprising. The theme of departure could also be a metaphor for death: all the imagery is easily applied to a death during the night, especially if the following lines are considered:
Saw morning harden upon the wall,
That your great going
Had place that moment, and altered all.
The narrator is "unmoved" because he is accepting of the death. Later he "seem[s] but a dead man held on end / To sink down soon...." This can be an example of the commonality of elderly couples to pass away close together, as one death takes away the other's will or reason to live.
The other major theme, of yearning, is shown in this stanza:
Why do you make me leave the house
And think for a breath it is you I see
At the end of the alley of bending boughs
Where so often at dusk you used to be;
Till in darkening dankness
The yawning blankness
Of the perspective sickens me!
His yearning is so great that he ascribes her memory to fleeting glimpses of people in the distance; this is also a common reaction to death, and can be frustrating and depressing for people who see their loved ones in others. There is also the unspoken hope that one day (if the woman is not dead) the person standing in the dusk will actually be her, giving his frustration a small glimmer of hope.
(ALL QUOTES: Hardy, "The Going," poemtree.com)