When our body speaks, we need to listen. Not being able to think or expand on our thoughts properly, is a clear indication of fatigue.
Most drivers have a set of tools.
And most drivers take excellent care of their tools. Our body is a tool that we use in our work, yet we take better care of our tools that we keep in a box than we do the tool that is our box. A driver from Jackson, MS was headed toward Seattle, WA on Interstate 90. It was cold outside and he was glad his heater was working properly. He had been on duty past his allowed hours of driving, but since he only liked 75 miles, he knew he could cover the log book.