The symbol that we know as Yin Yang is, more properly, called Taiji. The symbol represents the principle of opposites: hard and soft, fast and slow, day and night, male and female, etc. The art of Taiqi is also named after this principle. When people think of Taiji , they often think of people moving slowly but that is only the first stage. In Taiqiquan we first practice soft and slow to learn to relax and to learn good posture - this is the Yin. Later, we are taught to move faster and how to strike and throw whilst still remaining relaxed - this is the Yang.
The video below show Grandmaster Chen Zhenglei and a granddaughter (maybe his - my Chinese isn't good enough for me to be able to tell) doing a dual demonstration. The Grandmaster starts by demonstrating some slow forms and then he finishes by demonstrating some faster techniques. You can see that he remains relaxed even when he's jumping. The Yin is always present, even when he's expressing Yang and vice versa. This is an aspect that often gets overlooked by many teachers.
This Monday is a full moon so we'll be taking it gently & working on the 'feel' of the moves. We'll finished with some Qigong.