Anticipate everything, anticipate nothing
The point of this story is that we can spend a lot of time envisioning specific situations and devoting our energies to solving problems that may never occur. It is much better to go into a fight with an open mind and general strategy than to plan for a specific occurence and be defeated. Train yourself to parry attacks and then riposte; not to parry an attack that is just three inches above your right elbow with a riposte to the opponents third rib. This situation may never occur in a fight so will remain essentially useless.
This is a philosophy for life in general; it is much better to have minimal expectations and a general strategy rather than specific hopes of one unique outcome which are ultimately unfulfilled.