While the use of visualization can improve physical performance, constantly imagining fighting any specific person, or group of people, every day, is not condusive to good mental health. Instead, assume the existence of the Grey Man. He is grey because he belongs to no race, class, or clan. We refer to him with male pronouns, but he just as easily could be a Grey Lady with no real loss of meaning. He (or she) has no face; only a form and figure. He’s roughly your height, and your build. He is a featureless grey figure, like those guys in zentai suits who turn up at sporting events.
The Grey Man does not tip his bartender; he abuses women, and borrows tools without asking. If he has friends, he’s always asking them to lend him money, which he then promptly spends on scratch-and-win lotto tickets. In his personal dealings, he takes the time to express every flavor of bigotry. He has developed no skills, learned no trade, and enjoys no hobbies, since he prefers a life of unconstrained leisure, and would rather sleep than be successful. He never returns favors, he pays no attention to what he eats, and he doesn’t care when his partner doesn’t orgasm during coitus, as long as he can. He watches others work, and tries to take credit for it later. He complains about the political process in which he does not participate. He doesn't spend with his children. He blindly obeys authority -- and all those who claim authority -- attacking anyone who questions the legitimacy of power, only to remain silent and milquetoast when that power is inevitably abused. He talks big, and then immediately makes excuses. He has no time to read, but makes the time to watch four hours of television every evening. He never sweats at the gym; he only goes there to socialize, and to make unoriginal insults behind the backs of the people who legitimately want and need to use the machines that he is resting on. He refuses anything that can save money in the long run if it requires a capital investment now. He holds that the only value that anything can have is its current market rate. He considers his employees as nothing more than nonlinear programmable actuators. He has no scars on his face, and he cannot handle pressure. He uses sex as a weapon to manipulate people, or as a cheap thrill; giving no thought to the emotional baggage that could ensue. He wants to cut out of work early, and he wants to close down a bar when he has to work the next day. He feels no passions, and tells no tales. Idle threats of violence are his standard way of dealing with problems. If that fails, then he abandons his problems, leaving them for others to solve. He only values money, status, and power; and seeks them only for the sake of obtaining more money, status, and power.
The Grey Man is the anthropomorphic representation of everything you hate about yourself. He is every one of your bad habits, negative thoughts, regrets, and self-doubts which has taken on a human form to literally attack you. If there is one person you have to envision yourself fighting and crushing, over and over, many times, each day -- please let it be your personal Grey Man.
Every time you stop fight him, he gets a little bit weaker, and you'll get a little bit stronger.