The journey in Christina Rossetti's poem "Uphill" can be read (and generally has been read) as an extended metaphor for life. The clearest implication is that life is hard. The journey does not slacken or get any easier. One must travel all day without respite. The only rest is at the inn of death, and when you reach the inn you must rest: there is no avoiding it.
Only at night, after death, will the traveler meet other wayfarers. This emphasizes the loneliness of life. Rossetti takes the Christian view that life is merely a preparation for death, which is why only one of the poem's four stanzas deals with life. The traveler is assured of a bed (the inn of death is never full, though a final destination, such as heaven or hell, is not mentioned) but not necessarily comfort, merely "the sum" of labor, which presumably means whatever he has earned through the manner in which he has conducted himself on life's journey. At any rate, the uphill struggle is over.