Many people like to drink coffee because it makes them feel spiritedness. For instance, usually, a lot of salarymen prefer drinking a cup of coffee before they begin working or when they're forspent.
It seems that is the purpose of drinking coffee for many people. However, does it work? Probably it did work for most people, though, for me, it doesn't work at all. Even if I'm bushed, a cup of coffee still couldn't refresh me. I've tried that before, but it just didn't work. I don't know why.
Then, how do I deal with this kind of problem if I feel tired. Well, I would go to sleep rather than drinking coffee because I know it won't help.