I've never heard that expression used idiomatically, but if it is, it is obviously referring to paying too much attention to what's behind you (including past experiences) when you should be giving your full attention to what's in front of you.
It doesn't seem to be an idiom. I think it's just a figure of speech to make the writing more dramatic -- the person's eyes are "darting," meaning they move rapidly back and forth from the road in front to the rear-view mirror of the car, or to the rear-view behind them.
Go look in the mirror and make some faces. See how your mouth screws up? To make a mouth is to make a face, usually an unhappy one.
Go look in the mirror and make some faces. See how your mouth screws up? To make a mouth is to make a face, usually an unhappy one.
"Darting" means moving rapidly from one place to another. If your eyes "dart," then your gaze is rapidly shifting from one point to the other.
A way to develop a good facial expression would be to practice in a mirror. Find an image of a good facial expression you would like to mimic and practice it over and over again in a mirror until it is natural.
Mirror is a symbol of celebrant's beauty (inside and out).
Full Length Mirror
The German word Spiegel translates as mirror.
Kagami
The correct expression is "the eyes are the window to the soul." This means that a person's eyes can reveal their true feelings, emotions, and intentions.
It's a "full length mirror"!
reflect like in the mirror
Sei hansha