Sensei Sandeep Desai on the 70 % threshold in Taoism...
https://www.speakingtree.in/article/the-70-threshold
QuoteAt the heart of Tao philosophy is the 70% rule. It states that you should do a T'ai Chi movement to only 70% of your potential.
Striving for 100% inherently produces tension and stress because when you strain yourself, your body experiences fear. Even without you being aware of it, your tense body responds by shutting down. At 70% capacity, you can throw 100% of your energy and effort into practice, and you still generate 100% of the possible Chi that a T'ai Chi movement is capable of producing.
Going beyond 70% drains your energy reserves. Staying within 70% of your capacity produces optimum physical accomplishment, simultaneously reducing psychological stress. The more you relax, the more energy, stamina and strength you will have.