Do Not Move Your Head
Many beginners, when they start doing Chi Sau黐手, will move their head when they are attacked. Of course this is quite normal for a beginner as who is not afraid of being hit? However, in Wing Chun training we need to face it, even if the fist is very close to our nose we need to look at it, not move our head or upper body. If we do not flinch and move, it shows we are not afraid and so our mind can be clear and we can relax. When we can relax, we can move our legs and use our footwork. Moving the legs is better than moving the head as this means you can maintain a distance from your opponent and that your hand positions will be good to allow you to attack and defend. When you move your head you can avoid the first attack, but you will fail to avoid the next one because you are still in the same position only with a deformed posture.
By practising Chi Sau with your Wing Chun brothers and sisters you are safe and so you can develop your skill before you go to Chi Sau outside or have to defend yourself!