The emotion linked to this quote is quite mundane. This is because during September the sky gets dark quickly. This is also reflected in a later line. 'The dark of the ground seemed to drink the light of the sky'. This could also foreshadow that something bad is about to happen.
'It was a late September'
This interrogative phrase is very effective as she is asking a rhetorical question because she knows the answer but she can't face up to it so she is questioning herself. She may not also understand how her husband is hanging 'fairy lights in the tree'.
'Is he putting fairy lights in the tree?'
'I made him sit on the other side of the room and keep his hands to himself.'
In this imperative quote we understand how she is feeling without her saying the words. The fact that she made him sit on the opposite side of the room implies that she doesn't want to be anywhere near him, which means she must be quite angry with him
This short declarative phrase adds a lot of impact in emphasising it. It again reinforces the fact that she wants to keep as much separation from him as possible.
'So he had to move out.'
'So he had to move out' is a short and concise sentence and clearly sums up what happened next. This suggests to the reader that this happened without an argument.
This is what the speaker - Mrs Midas - feels about her husband's poor choice. She felt that he is selfish because if he treasured the moments they spent together then he wouldn't have accepted the gift. This is all said in the succinct choice of lexical items - 'Pure selfishness'. Also the full stop at the end add impact to what she is saying and reinforces the succinctness.