Imagine the physical action to grasp the shock or surprise element.

Visual Imagery

It's often used to intensify a reaction, but the jaw doesn't literally drop.

Exaggeration

Use it to describe an emotional response, not a mild or indifferent reaction.

Understand 'jaw sagged' implies a slow, heavy reaction, unlike 'jaw dropped'.

Recognize that 'jaw sagging' fits somber or serious disappointing moments.

Reflect on how the physical expression mirrors a feeling of being burdened or let down.