Sponsored content. Us Weekly receives compensation for this article as well as for purchases made when you click on a link and buy something below. Picture the scene: alarm goes off, smartwatch buzzes with the usual summary. Sleep, decent. Resting heart rate, normal. Activity rings from yesterday, closed. Every number checks out. And yet the morning feels wrong in a way none of those numbers explain. Tired in a way that “7 hours of sleep” doesn’t account for. Sluggish through a workout that should’ve felt routine. The instinct is to shrug it off, since the numbers all look...