It's a great topic. Many people like to take things to the extreme. If something is good, more must be better. In Kung Fu, (and life) it's just not true. The yin/yang sort of show this but in a different perspective. That in the extreme, you get to the slight of the opposite. Also, that in everything, there is a touch of the opposite.

For me, I've been using the phrase, "It's all about the baby bear" Stemming from reading to my children, it's not too hard and not too soft but just right.

In Hung Gar, this is captured with one of the 12 bridges, Lau Kiu. Translated as reserve, it exactly means that you are straight but not straight, bent but not bent, etc.