1. Evade a Strong Force
There is a limit to how much force any particular technique can handle. No matter how strong the stance or how precise the angle of the hands, there will be a force strong enough to get through. Master Wong Kiu expressed this thought by saying "You cannot block a motorcycle with a Bong sau." It just can't be done.
Wing Chun teaches some direct confrontation techniques in terms of blocking kicks or roundhouse punches; however, when the attacks are too strong, then alternative methods must be used. The advantage of direct confrontation techniques is that they are faster than going with the flow methods.
One of the best remedies against a strong force such as a spinning kick or wild hook punch is not to be there when it arrives. You always risk getting hurt when you clash with a strong force.
2. Combined Strength
There is a Chinese term called "Garb Lik" which means combined strength. This term means not to have one passive hand and one active hand. For example, don't hold someone's arm with one hand while hitting high and low with the other hand. The holding hand is passive while the hitting hand is active.
The punch at the end of the second set or the Bong sau actions in the second set illustrate the combined strength concept. When you punch, there is also an equal strength put into the Wu sau or Guarding hand. When you apply the Bong sau or Wing hand, you also put a strong instantaneous force into the guarding hand.
In the double sticking hands, when you do a center palm hit, don't have a weak high Fook sau or else the opponent can hit you by changing his Wing hand to a neck chopping hand. Always have "Garb Lik" in all of your actions.
3. Use Body Position
During fighting practice, the opponent may have you jammed up so that your hand actions cannot be applied. In such cases, a shift of the body can sometimes change the angles in such a way that you again have room to maneuver.
If shifting does not help, you may still be able to move the stance in such a way as to offbalance the opponent. Even a slight change in position can sometimes give you another chance to hit.
Seemingly hopeless situations, such as where your opponent has grabbed your kicking leg, can sometimes be remedied by changing the body position. In this case, dropping to the ground in order to kick the opponent's joint with the other leg.
In Wing Chun, it is not only the hands which provide shocking forces. When you are being trapped, violent rotations of the body combined with the use of the elbow can sometimes save the day. Think of trying to hold on to a wiggling fish.
4. Be Direct
There are sayings in the martial art world such as "Use Soft Against Hard" and "Go With the Flow." These principles are useful when handling large forces. When the forces are not large, such as the case of a roundhouse punch thrown by a similar sized opponent, it is often much quicker to clash directly with the attack so that you hit the opponent immediately.
If you are confident with your technique and can handle the opponent's force, then you can just charge in directly to the opponent's center. Provided you are able to keep to the center, you will have no problems.
Use common sense to figure out under what circumstances the general principles of Wing Chun apply. These principles were often sayings to help people remember what to do. If you stick too dogmatically to a saying, then you could also be done in by it.
5. Restrict Movement
The most dangerous opponent is one who is at close range with free use of both arms and legs. At high speeds it is not possible to predict or deflect all attacks. You are bound to get hit. World champion boxers are not able to avoid all hits.
When in close contact with the opponent, try to restrict the opponent's movement. This increases your chances and decreases those of the opponent. Use one arm to control two. Use Gum sau or Pressing hand to control the elbow of the opponent. When at close range, use your leg to trap the opponent's leg so that he cannot kick. There is a famous saying, "Allow the opponent's useless actions, but prevent his useful actions." If you try to control the opponent totally, then he will fight much harder than usual.
The Wing Chun Kung Fu Digital Library