Today I learned (again) the benefits of adequate rest.

Coffee won't help you as much if you're tired

It may sound counterintuitive, but caffeine, which made its name as an accessory to sleepless nights, actually works best when you’ve had some rest. This comes down to the drug’s chemistry: Caffeine mimicks the shape of a naturally occurring brain chemical called adenosine, which Braun compares to an internal “brake pedal” that allows us to turn off and fall asleep. By essentially clogging our adenosine receptors, caffeine plays defense for stimulating brain chemicals such as dopamine, allowing them to work without the crank-down effects of adenosine. But caffeine won't do as much for you if you're so tired that the chemicals it's clearing the way for are already depleted.

“Caffeine will work best when you already have high levels of these accelerants, like when you’ve had a good night’s sleep or had a nap,” Braun says. “If you’re really sleep-deprived, you won’t get the full benefit of caffeine.”

We might have been through this before but I didn't realize till now that coffee helps less if you're tired. Got any more information about that?

Don't drink caffeine after 5pm. 

http://www.businessinsider.com/what-not-to-do-before-you-go-to-sleep-2016-3