Stress
Get those meditation classes scheduled and order extra stress balls, because this job's a stressful one. This isn't something people do their entire lives—the human heart simply can't handle it. Some days will only be a lot of hard work; others will leave you demoralized beyond belief and staring at the bottom of a pint of Häagen-Dazs after work.
Stress can be magnified by an employer who yells and shouts while you're slaving away cooking their food and cleaning their kitchen—and even feeding them airplane-style if that's what they want. And that may actually be what they want—celebrities can be weird.