Namaste' Virtue121
To answer your question, which is a good and important one, will quote Wallace Black Elk, a Lakota Medicine Man who passed on a day or two before or after my own father. I have learnt a lot from this man and his method of running a Sweat Lodge is the basis of how I run my Sweat Lodge Ceremonies.
So where does evil get it’s power?
It comes from us. It crawls and creeps into our brains. We twist our own minds. We take that sacred knowledge and use it to fashion a gun. Then we call that knowledge power. So there is all this traffic between our ears, and that is where the evil comes from.
By Wallace Black Elk
So basically evel comes from our own mind ramblings, which is why it so important to have clear thinking, mind control, and full awareness of everything we think and do. It is fine to have habits and cellular memory to keep our actions smooth, but we must not be on total auto pilot; we must be aware of every little detail of our thinking, actions, and intentions. This is the porpose of meditation; to have the awareness and control of our thinking processes, which the govern our actions. Intention comes from have a strong connection to Great Spirit, so that we can be doing His will.