Remaining stoical when suffering pain or discomfort is not the right approach.
It is far better to be honest.
Honest with yourself, with your training partner, and with Sifu.
If you need someone to ease-up, slow-down and be gentle... then just say so.
This is not a sign of weakness. We are all vulnerable.
Instead, it shows that you are sensible and recognise that you are indeed human. That's ok; we all are.