Greatest Opponent of Strategy

          Strategy is effectively mastery, as that word, that want is always implied, yes, in that way of usage, at the leasta.
          To retain/achieve high mastery, the pitfall before the final stage can be quite well concealed and in least expected places and times, and timings.  (this pitfall is): The greatest opponent of strategy would have to be: arrogance.  Whether arrogance from friendlies, arrogance from enemies, or arrogance from self and etc and so on.

Arrogance makes the man hasted to make a decision quicker than ready. Like taking the chicken out of the oven too early - it ain't gonna be good!  Or, quicker than ready for the chef's instruction learning - skips the instruction for cooking chicken in oven too quickly, missed a major step listed, and the similar result comes later.

One way to counter in case of unsuspected self-arrogance, would be taking use of reserves. Having some reserves in case of an emergency trial. (or emergency situation pop up, in other words)