Raise your hand if this has happened to you: It’s 8 or 8:30 in the evening and you brew a cup of bedtime tea full of relaxing herbs that will surely guarantee a good night’s sleep. You sip it as you tidy up and change into PJs, taking the last drink just before you brush your teeth. Lights out at the stroke of 10, you’re calm and perfectly sleepy, drifting off with the satisfaction that you’ve set yourself up for the elusive eight hours—only to wake at 12:24 a.m. with the undeniable urge to pee. Resigned, you get out of bed, visit the loo, and tuck back in. Then lie awake for an hour or more, waiting for sleep to come. Foiled again.