Everybody has that computer that pops up with a "system update" every once in awhile. The one that you click and your computer has to reboot and your work is pretty much ruined for 30 minutes. If you are like me, you ignore that reminder to "restart your computer." A few months later you notice that it no longer is working properly and its gained 20 lbs (or at least it is running like it gained 20 lbs). This is pretty much what happens when we do not sleep well. We do not give our body that time to "install an updated version." All of this happens when we sleep!
