I'm really gullible as well so, I own up, I have actually checked my bed sheets because of that mite one (only they weren't flesh-eating, I'd never have believed that, unless I was in some hot country...) Someone said it to me years ago, and not that long ago I felt a bit itchy in bed so I got paranoid and inspected my sheets minutely for weird bugs. Obviously there were none.
Make them a calendar from an old calendar (Ex. Use August from last year for April of this year -- same days except there is one extra -- cross it out). Scribble "Every Day is Rachel Day" in large purple letters. Also, write in "...Except Meat Day" on Easter, cause the ISTJ has been dutifully abstaining from consuming meat on Fridays due to his moral code.