I can have trouble sleeping and have to battle fatigue at times. Not long ago I crunched the bumper of my car into the side of the garage because I was too mentally fatigued to drive. Didn’t do a lot of damage, scratched the bumper and did minor damage to the the wall, but something I would have never done if I was properly rested and alert. Mental fatigue is a strange thing, it can make you fail in performing simple tasks you do routinely.