In My November Guest, Frost is suggesting that sorrow allows people to see different kinds of beauty or beauty in different places and events than what had been the case before they became acquainted with sorrow.
The poem is filled with descriptions of sights and sounds that are not usually associated with beauty - "the desolate, deserted trees, the faded earth, the heavy sky." Most readers would associate these images with sorrow and sadness, the bleakness of a November day. Sorrow, the new presence being described by the speaker in this poem, appreciates these as being "beautiful as days can be" and delights in being out in the weather, observing what many would characterize as dreary rather than beautiful surroundings.
However, the last stanza tells us that the speaker in the poem has come to understand "the love of bare November days" and recognizes the beauty of its own kind contained within the sorrowful time that brought November into his life. While he is sad, he acknowledges the beauty in some aspects of his situation.