“I adjure you by the Jesus whom Paul proclaims. Seven sons of a Jewish high priest named Sceva were doing this. But the evil spirit answered them, “Jesus I know, and Paul I recognize, but who are you?” (Acts 19:13-15)
There is always the potential for problems when we work with borrowed tools (q.v., 2 Kings 6:5). And these seven sons of Sceva were doing just that: using borrowed tools. When it's not our own tool, we may not be familiar with how it functions. We make assumptions and operate with limited knowledge--an easy recipe for disaster. For Sceva's sons, the result was disastrous.
To have victory in spiritual warfare we must understand, own, and walk in what we know. When we understand the nuances of spiritual warfare, then as we engage, we are not just mimicking something we've seen or heard about, but are functioning with confidence and walking in victory because we are walking in what we know.