There are seasons in a Christian's life when they will have to fight spiritually. Satan and his agents are cunning and will stop at nothing to see us fail. That's why its important for us to put on the armor of God through faith daily. And, I went through what seemed like the worst season of my life. I had to learn to fight spiritually (praying more, reading more, learning how to use the word of God, using my authority). It was difficult. Some days I felt like giving up but God would speak and encourage me. During that difficult time, I learned some of the tricks of the kingdom of darkness. One of the most profound things that I learned is that demons are legalist. They sit and wait for us to open a door. Any doors can be opened through what we say, our behavior, and most of the times its through ignorance. Then, I learned that the enemy has no power unless we give it to him. If no door is opened, then how can they rule? They simply cannot. Just like a virus they need a host to live and do their dirty work through.
And, the enemy doesn't just attack ministries, he attacks people health, their identity, finances, family etc. Anything to make them stumble and fall. And, the worse part of spiritual warfare is not knowing who you are Christ. If people knew who they were during the battle (victorious), then they would not be moved by everything that comes their way.