Morally every creature has a right to defend itself and use force to do so.
However a creature does not have a right to take things from others.
Good people protect good people from bad people.
Bad people take things from good people. It can be subtle, like insulting somebody to lower or take things away from them, so the bad person is then relatively better than the victim.
So need to love good and hate evil. Must realise though that evil is part of the one and so self, because all is one. However if evil, for the sake of the whole, it still has to reform itself or go.
Ways to win
Only start or go into a fight if you know you will win.
Never act out of spite
Never act out of revenge, old chinese proverb, someone who goes out for revenge should dig a grave for themselves as well as the other person.
Justice is fine as it is for others, not for yourself. Karma happens naturally from God, everything has consequences. It is especially needed if a person will not accept they have done wrong, so that they learn the lesson that they should not do it. It is fine if it is deserved by the person who has done wrong, but not if there are mitigating circumstances.
Need to have courage and bravery, this is an emotion as well as an intellectual concept. That is why people who are not aware of their emotions cannot do it.
To fight need to get angry and hate what need to destroy. This is because they are emotions and feelings about destruction. This also helps get past the fear of not wanting to hurt oneself.