Looks a bit sad, probably because today is Friday and Friday means it's fish pie for dinner. No one likes fish pie, especially when the wife's so bored of making it and life she can't be bothered to boil the potatoes properly any more.
At work the next day he lies about it, and says it was steak and chips. In his mind, it WAS steak and chips, so it's not really a lie.
We all have our own little coping strategies.