I don't remember if I heard this from voice teacher or thought it up on my own, but rather than thinking high for "high notes" and low for "low notes," I sometimes think of my voice as like a trombone. The slide goes out for the low notes and comes in for the high notes. Works for me.

Pitch—and any subtleties and nuances of tone—is a matter of mental image and being able to hear the notes you want to sing in your "mind's ear." Tension or any other attempts to control your voice with voluntary muscles actually interfere with it.

Don Firth