An impromptu snooze is a superpower, and the same methods can get you drifting off at night, fast. — This one’s a gamechanger. Productivity, alertness, memory, mood, vigilance and health — all improved by taking 25 minutes out of your day for a quick snooze. Let’s look at the whys, whens and hows of the perfect power nap, and how those methods can help you sleep at night, too. Why so short? …