Your images are out of balance.  Light and dark clash and destroy the harmony you seek.  Yin / Yang will help you restore that balance.  Quickly lighten and darken select areas in your images to add drama and shape the light.  Fill the shadows and tame the highlights.  Yin / Yang is your mantra and your tool.

See the power of Yin / Yang in this video tutorial.

Yin / Yang uses layer masks, but never fear – this article explains it all.

See user-submitted examples using Yin / Yang at the Recipes section.

Good Vs Evil is a TRA1 Photoshop Action that operates very similarly (with subtly different effects on the highlights and shadows).