When I am tempted, both the body and the mind say, "Do it! Do it!". I can't do anything but pray to God and say, "Lord, I really want to do this evil thing. It seems so good and necessary." But I know in my Spirit that it is not good for me. It will not help me. It will only rob my joy and leave me defeated. It will also cause me to look to other things rather than God and Jesus for my enjoyment.
I would think that the mind at least would be on my side against my body and my emotions, but no! My mind is part of my body. It is right there inside my body. I tend to think of my body as from the neck down. Actually my body includes my brain (mind) too. There has to be something separate from my body and my mind that is present that can say, "Hey. This isn't right! This will not help me and is not good!"
I know that Paul says in Romans that the law of his mind wages war against the law of his body. I think this is talking about the unregenerate man whose mind is informed about the law of God, knows that it is wrong, but does it anyway because it really wants to do what the body does (since it is the body anyway). There has to be something else. I don't know how all that works, but Paul says in Romans 8 that the mind set on the Spirit is life and peace. So, somehow, those who have the Spirit of God have some kind of principle in them that connects the Spirit to the mind.