Practical Solutions for Encounters with Invisible Demons – Megillah 3a lines 41-44
Later on Megillah 3a we have an amusing take on why we sometimes get spooked for no reason. Long story short, the Talmud seems to think that when we are afraid without seeing anything, it's our mazal that saw it. Rashi helpfully supplies that this mazal is "שר של כל אדם למעלה — guardian angel of each person up above." Always looking to the practical, the Talmud then asks "מאי תקנתיה — what is the solution to this problem?" Say Sh'ma, of course! But if that's not possible (or if it doesn't work), there's still a way to survive this attack from an invisible demon. Simply say "עיזא דבי טבחי שמינא מינאי — the goat in the slaughterhouse is fatter [tastier] than me."