In the Beginning Was the Word, and the Word Was Suck: A Guide to Truenamers

[willpell]

Then how do you not have to make will saves against cure spells cast on you? They allow a save but as per the voluntarily failing your save rules you don't bother because you trust your cleric that it will not harm you.

Cure spells are not capable of harming you (unless you're undead). Presumably your subconscious mind, or whatever else governs your instinctive resistances, can understand this, sensing that the incoming influence is Harmless and not resisting it. You can save against such effects, but only intentionally. Whereas any Harmful effect always gets a save unless you voluntarily decline it, and no compulsion can interfere with that "voluntary" part.