Yin = Feminine, Dark, Negative, Soft, Yielding, Resting, Cold.
Yang = Masculine, Light, Positive, Hard, Thrusting, Active, Hot.
According to the I-Ching (pronounced "ee jing"), all of existence is an interplay between yin and yang.
So how can yin and yang theory help me with my life? Simply put, utilising yin and yang will allow you to look more completely at a situation or problem. Very often, we tend to have one view.
For instance, if our car which refuses to start, we focus on what is wrong with it (inactive - yin). However, it is also worth identifying which parts of the car are still active (yang), and by process of elimination, can ascertain which part needs fixing. We can also remember back when the car was last working (yang), and work out what has changed since.
Yin and yang theory also states that when going extremely yang, you eventually become yin - and vice versa. To keep the car example - a car will get you from a to b very quickly (yang). However, if everyone wants to go the same way at the same time, traffic jams occur (yin) and it's quicker to walk.
If you have any questions about yin and yang theory, email me.