In the Martial arts it is the practice of eliminating distractions.
You focus on a single action, breathing, and eliminate all other thoughts.
No past, no future, just that single breath as it happens.
So it should be when fighting.
Distractions are a hindrance. Any thoughts of what has happened or what you intend, will take seconds away from your ability to react to what is happening now.
The past can not be undone.
The future is determined by the now, so what is most important is acting in the present.
Meditate to focus on the present, to strip away distraction, to act more efficiently for the future.
"Stop thinking, and end your problems." - Lao Tzu