Where The Shoe Pinches
One of my creative writing exercises reflecting on the meanings of idiomatic phrases and expressions.
Generally, if you are wearing shoes or boots that pinch at the skin on your feet, you know at which points the pain is apparent. The shoe might scrunch up the toes or the loose heel might scrape at the skin on the back of the ankle.
Similarly, in life, we know the factors that can ruin an otherwise perfectly good day; we wanted toast but the bread had run out or gone mouldy in the bread-bin. The cat dragged a mouse in and you had to clean up the mess, etc.
The pinched shoe-point is the focus of blame, and generally a genuine one. It may be a person who is the pinching shoe; someone failing to keep an appointment on time or not paying back a debt you hoped to have settled, a partner forgetting your anniversary, or birthday, etc.
Some pinching shoes are easier to change than others.