Our core natures and personalities reflect Yin and Yang. A person who is shy and inward would be said to have a yin personality. An outgoing, assertive or aggressive individual would be said to be more yang. Of course, our personalities change throughout the day and over time. We all go through yin phases and yang phases.
Our personal relationships also manifest the principle of Yin and Yang. Sometimes we dominate another individual and sometimes we are the dominated. Sometimes we are the giver, and sometimes we are the receiver. Giving and receiving in life are but a reflection of the universal Law of Yin and Yang.
Yin and Yang is a concept of relativity and each person must be looked at relatively. An aggressive person with a hot temper would be considered to be of a Yang nature, irrespective of gender. A cold, inward, passive person would be considered relatively Yin, irrespective of gender. A person who is dry (Yang) will need to increase their fluids and blood (Yin) and a person who has cold extremities will need to invigorate their circulation and metabolism by increasing Yang, in order to establish a healthy, balanced physiology.