Paul encourages us to use all the tools at our disposal, because Satan has developed strategies against us. The purpose of Satan's strategies is to take glory from God and to make our lives miserable. People were designed to live in joy and peace; if Satan can get us to live without joy and without peace, he has succeeded. MIsery per se is not really necessary. He has moved us away from our design; he has stolen glory from God.
MAny people reguard Sata's plots as actual attempts by Satan to harm us, our family, our friends, or our property. I certainly do not mean to say that if Satan can do any of these things, he will not. What I am saying is that for far too many of us, he does not need to. All he needs to do is whisper about some problem, some worry, some concern, and our minds filter it through a non-God grid. And we roll it around in our brains. It is not prayed over. It is not considered in the light of what scripture says. It is certainly not regarded in a way the brings purification of our hearts and minds -- as scripture promises that any trial will.nor is it regarded in the light of God's mission.
Rarely are any of these things done. And when we fail to shine God's light on circumstances, Satan wins.