The guys that drive for a living are limited to 13 hrs per day of road time, or they get into trouble with the Feds. "Road weary" is one thing, but driving tired has a hypnotic effect that turns you into a potential weapon behind the wheel. One "nod off" and a jerk when you 'come to, and you're in the ditch, or wrapped around a telephone pole.
Plan the trip so that you're fresh,and get the necessary rest. You're operating between 2,000 and 5,000 pounds of machinery that can devastate if you lose control.