Doing the right thing at the right time is all a matter of reading the situation correctly, and responding appropriately.
Initially, it is quite difficult. With practice it becomes easier.

Learning to follow and exploit the line of incoming force is paramount.

If you make the wrong movement, you will find yourself locked into a contest of strength.
Remedy it by using the three dimensions. 
A person cannot have strength in all three directions simultaneously.
Change and you will find their weakness.