No matter what anyone says, driving is tiring. It doesn’t have to be 6 straight hours, it could be 6 consecutive trips of 15 minutes each. You’ll get exhausting.
That being said, I love driving, but following traffic laws, watching out for idiots on the road, paying attention to the GPS, choosing the most efficient route to get there faster, being cautious (and also have a little fun, of course). You realize how tired you are when you finally finish everything and sit down. You will see that parts of your body will be sore.
I must admit, I get quite tense while driving, not in an irresponsible or forced way. But I am 100% aware of what happens inside and outside the vehicle. I know what is going on 5 cars ahead, and 2 cars back. I imagine a route in my head, and I run it in real life, either at full speed or relaxed speed; like a simulation but with consequences.
An instant maneuver could save lives. Beyond luck and reflexes, there is skill and prevention. When you’re driving you have a fraction of a second to react. There is no room for mistakes, they are costly and dangerous.