It is saying that in the first paragraph that he is looking out of his room into the world and all he sees is the world calm and peaceful throughout the land. He looks up in the sky and all he sees is the star in the sky that he thinks thats his wife looking down on him and watching him that how he lives with her being gone.
The second stanza said that he deprived him self from all his meaning behind his things. Behind the sad face she is thinking things from the past. He is thinking about his lost love.
In the third stanza He is talking to his wife in his head. He remembers in his head that his wife is an very sweet and caring person. He was comparing the planet calmness to his wife. HE gets depressed through the days of thinking about his wife. Dark shows more the more you think about her.
In the first stanza when it says.LO! in the painted oriel of the West. Whose panes the sunken sun incarnadines is imagery and an metaphor. ITs this because it saying that he is having a memory and that he is looking into like his own little word out the window and looking a through the glass of the window all you see is calm outside and and bright things.
In the second paragraph where it says Like a fair lady at her casement, shines The evening star, the star of love and rest. This is an metaphor because its comparing an girl being comfortable at her house and being her self to a star in the sky saying that it is comfortable there and that you can look at it and make you calm and make you your self and to him the star reminds him of his wife.
Behind the sombre screen of yonder pines, With slumber and soft dreams of love oppressed. It saying that it is an metaphor and that he is saying that he was once alone and every time that he had a memory of her he would go further into depression.
My best and gentlest lady! even thus, As that fair planet in the sky above, is a metaphor it is comparing her sweet and caring nature and her self reliance to an planet saying that the planet is calm and that every time he thinks about her and looks into the sky he sees this planet.
Dost thou retire unto thy rest at night, and from thy darkened window fades the light. Is an Metaphor due to that he doesn't ever quit thinking about his wife until he sits in his bed and goes to bed. The more he thinks about her the more dark comes in because he is depressed and control his emotions.