"Our struggle is not against flesh and blood, but against the rulers, against the powers, against the world forces of this darkness, against the spiritual forces of wickedness in the HEAVENLY PLACES" (Eph.6:12).
3500 years ago, Moses came down from Mount Sinai and brought the Israelites a promise from God of a kingdom on this earth. But 2000 years ago, Jesus came down from heaven and brought us the promise of a heavenly kingdom. This is the fundamental difference between the new covenant and the old. If we don't understand this, we will not be able to wage an effective warfare against Satan.
Our kingdom is not of this world. And so we must NEVER, NEVER fight or quarrel with human beings concerning any matter. This is the Number One requirement for effective spiritual warfare. One of the chief ways by which Satan tries to sidetrack believers from their calling, is by getting them to fight or quarrel with others - with their relatives or their neighbours or their brothers and sisters. And invariably the quarrel will be concerning some earthly matter. Thus he succeeds in dragging believers down from their heavenly position to this earth and its affairs, and thus makes them ineffective in their battle against him.
If you want to fight Satan effectively and to build the church, determine that you will never get involved in a dispute with any human being, or concerning any earthly thing. We must not even wage imaginary battles in our minds, with others. We must not have a single complaint against anyone.
And we must not have an inward demand on anyone either. We must not, for example, have a demand that people should treat us with respect, or with consideration, or show love to us, or that they should never cheat us or deceive us etc., We must not have such expectations even from our marriage-partners. All such disputes and complaints and demands are indications that a person's kingdom is of this world, and that he has given place for Satan in his heart. And such people are doomed to live a miserable life.
God is the Only One with whom we have to do (Heb.4:13). All our circumstances (including the way others treat us) are designed by our loving Father for our very best - to conform us to the likeness of His Son. Therefore we have no room for any complaints against anyone, but plenty of room for praising God at all times.