the more steps you take to "prevent" being manipulated, the easier you are to manipulate. The easiest people to control are the people who think they're immune to it.
It seems to me that those are two entirely different things. I am taking steps to prevent being manipulated (like learning a lot about manipulation, psychology, trance etc.), and of course it helps me not get manipulated as much as I used to, but I'm absolutely sure I'm not immune at all.
Like, I remember when a communication trainer shut me up by sending me into a trance a few years ago, and he'd have a hard time doing that now because by now I just know what he did there, and my awareness of my own inner states has grown a lot. And on the other hand, I know a few things that will shut me up, and I'm working on them.