“Her eyes darted left and right.”
“His fingertips fell to the table.”
“Their arms dropped.”
You might not see it (heaven knows I miss it in my own work more than I care to admit) but the body parts in the sentences above are not behaving normally.
Time to nitpick 🙂
It isn’t our “eyes” that “dart left and right” but our gaze – our eyes stay in our head (or should most of the time).
“Fingertips” don’t fall off our hands and land on the table – but we might drum our fingers on the table or bang the table with our fingertips.
And finally, if our “arms dropped” off (much as our fingers did above), we’d be walking torsos with no arms. Perhaps those arms might flop to the side.
There’s a distinct difference between being casually or clearly descriptive in the way we phrase what is happening. Being precise about showing an action can make the difference between having body parts doing unnatural things and painting a picture to truly capture the moment.
In your 2nd or 3rd draft, pay particular attention to how your characters’ bodies are behaving and double check that what you’re describing is actually what is happening and not just a way of saying something casually in every-day speech. You are a writer, and unless the sentences above are being spoken in dialogue, they need to accurately reflect what is plausible and actually happening.