Pick out several points that build up the idea of comfortable routine and a genuine looking forward to her husband's return.

Pretty much everything in the story paints a picture of a peaceful routine, all the way up until the husband reveals how tired he is (which he usually doesn't do) and when he consumes his drink faster than usual. I'll pull out some particularly quotable details and put them in bold text below.

To begin, the second paragraph of the story is filled with details that lead us to believe that Mary is happily, calmly living out the comfortable routine of waiting patiently for her husband to come home from work:

"Now and again she glanced at the clock, but without anxiety: She merely wanted to satisfy herself that each minute that went by made it nearer the time when he would come home. As she bent over her sewing, she was curiously peaceful. This was her sixth month expecting a child. Her mouth and her eyes, with their new calm look, seemed larger and darker than before."

As you can see here, Mary is sitting comfortably in a chair, feeling calm and happy that her husband will be home soon. Although the narrator doesn't say so explicitly in the above paragraph, we can tell that she probably does this same thing every weekday, since the next paragraph describes a routine:

"When the clock said ten minutes to five, she began to listen, and a few moments later, punctually as always, she heard the car tires on the stones outside, the car door closing, footsteps passing the window, the key turning in the lock. She stood up and went forward to kiss him as he entered."

The description above reveals how these particular actions are part of a well-established routine between the husband and wife. A few paragraphs later, we see some more details about their comfortable evening routine, before the husband starts acting noticeably odd:

"For her, this was always a wonderful time of day. She knew he didn't want to speak much until the first drink was finished, and she was satisfied to sit quietly, enjoying his company after the long hours alone in the house. She loved the warmth that came out of him when they were alone together. She loved the shape of his mouth, and she especially liked the way he didn't complain about being tired."