Are you a nightbird? I am so sleepy that I can't concentrate on work recently because of staying up late for seeing movie using cellphone. I think this is common phenomenon among young people. Staying up late is not good habit, it is bad for our health.But we can't feel a thing for short time, just sleepy in daytime. However, our health maybe have some problems like weight gain and reduced immune function. Consequently, I hope we sleep early and have enough sleep.