Practice with Sincerity

This is a new phrase I learned from Master Sun Lu Tang.
Practice without sincerity ? I have to admit there were days
that's how I treated Tai Chi.

Tai Chi's rule past down is 3 rounds or 40 minutes at my fastest pace.
Sincerity pace ??

I did 40 minutes of cloud hands again yesterday.
I felt the pulsing. That's sincere practice.

I feel the needles or ants after 5 seconds of cloud hands.
But only in left hand.