Strength is wrong

If you use strength then your energy will be expelled very quickly.  This is a serious concern if faced with a real life self defence situation.

This is also the case with over-extending, contracting or exaggerating; the attacker has more chance of harming you. 

Even in solo practice, you will be putting a massive amount of strain on your body.

Tai chi and baguazhang should be trained so that it is good for the body and can be practised into old age.