This could be mental tiredness or physical tiredness. Mental tiredness can occur simply due to the brain overworking at one point or working at a constant rate over a period of time. The brain is lazy like that, so it is used to recharging. It can also occur due to the late release of a chemical which stimulates the brain to feel alert. Physical tiredness can occur due to a lack of remaining energy (glucose etc.) in cells from exercising. Or muscle straining can also have the same effect.

We get tired, or become tired from all the stress we have on us or all the things you did the day you got tired. For example, you clean your house, decorate your house, throw a party, hang out with family and friends, and then clean up the party, put everything away and then whatever else needed to be done in that meantime. Well, your body wears off the energy that you woke up with, because sleep rebuilds your energy for the following day and it relaxes your body and mind. So with doing everything you do on a day, you will begin to become tired and need to rest by getting sleep. Now, how do people get tired from not doing anything, or just being bored. Well thats because your body is already in a relax mode, and your mind isnt fully set on whats going on around you, so your mind starts to drift away into a "day dream" and then you become sleepy because your already relaxed in a comfty position and your mind has already wandered off which causes a person to fall asleep or want to fall asleep. Its just like when your laying in bed before you sleep, you dream of something but at the same time your still awake until your mind fully wanders off then you fall asleep fully. Its the same concept for when your bored or havent done anything. I hope this answer was helpful, im only 17 and i know very much about alot of things teenagers dont know at this age. I hope i can help again.

People get tired from lack of proper fecal discharge. As they go about their daily tasks they are producing 2.2 pounds of feces in the intestines. Should the person not eliminate because of being busy the extra weight acts as an exercising weight and causes them to be tired. Proper discharge can overcome this so ask yourself, have I eliminated my 2.2 pounds of fecal materials today. And now you know, the rest of the story. (+5)