Ah, it's not exactly weakening, it's more like ... putting a cap on something to keep it from overflowing. It really only affects anyone with special talents or abilities. A normal person isn't affected at all. Rapunzel-chan might be affected by it, but I'm not sure how until she remembers more about her hair.
But she mustn't take it off! If she does, she won't remember anything she just learned until she puts it back on again.