Proper ettiquette or potential damage?

I do not know if its known but I'm not a practitioner of magick so many of the rules or ettiquettes are lost on me, so forgive my ignorance. I wanted to ask if using magick on someone, to help them or protect them, without their permission is possible. Because I remember reading somewhere online that the mind will instinctly block the energy of the spell because it doesn't know where that energy came from and will treat it like an intruder or something along those lines. Don't quote me on this, I could very well have misunderstood what i've read, or possibly the writer was wrong. I also wanted to ask about the dangers of using magick on people without their permission. Would it weaken the reciever? Make the reciever too dependent? or would something else entirely happen?

I should also add an exclaimer that I in no way intend to use magick without anothers permission (if I suddenly decide to pick up the practice). This is merely for my curiosity and I would appreciate it if anyone could clarify this topic for me.

Thank you.