In Japanese martial arts the word shin 心 may be used to described the heart and mind. Shin may also be loosely interpreted to mean 'spirit'.
While many martial artists are often greatly focused on the movements of their body to overcome an opponent, they seldom give sufficient attention to training their spirit.
In combat or practice sparring, martial arts practitioners also pay a great deal of attention to the movement of the enemy. One may wait for the opponent to move, or attempt to predict his his next. However, there is a practice that exists on an even higher level of perception.
In the concept of harmony or unity. When you are connected to your opponent's spirit you can feel his intentions and act to suppress his movement. It is not a fantasy. It is a highly fine-tuned perception of the opponent's psyche.
[ From a scientific perspective this skill may be explained by referring to psychological and physical patterns of behaviour in our opponent ]
Whichever way one tries to explain it, it is a difficult skill to master. It should not be neglected or put off till the later stages of ones development.
To be connected to your opponent's heart and spirit you must be relaxed and have mune muso 無念無想. The term mune muso describes when thought and action merge as one, without interference/distractions from the mind. Simply put, we must empty our mind of thoughts (mushin, 無心の心). You must also have the correct breathing rhythm, kokyu 呼吸 and your body should be in a natural posture. Do not even think about whether or not to strike. You will feel when your opponent has broken the harmony through his aggression. Then you will me ready.
With practice, sooner or later you will understand.