While driving long distances, it is very important to not go hammer and tong. Driving fast and hard is quite taxing on one's mind and can bring the onset of fatigue early. Of course, that doesn't mean one should drive slow. Just maintain a good speed and try not to fluctuate it too much. A secondary benefit from this is better fuel efficiency from your car, which means your driving range increases and you make fewer fuel stops, effectively making your journey faster.
Lane discipline is a very important aspect of highway driving and hence becomes critical when one is driving long distances. Switching back and fourth between lanes can be a pretty tiring exercise and this kind of strain is something you want to avoid for the long haul. Following lane discipline keeps you and other vehicles around you smooth, which also helps relax you when you are behind the wheel. Once your actions are predictable, it increases the safety margins on the road as well.
This is a skill one needs to develop while munching the miles on highways. Reading traffic is something that will come with experience, but it needs an active involvement by the driver. Once you are able to predict how the traffic around will flow and what are the intentions of the vehicles near you, it will be rather easy to figure out the path of least resistance through it all. This will greatly reduce stress and keep your fatigue in check, making it easy to drive longer distances.
Relaxed body, relaxed mind
On another note, while it is important to stay relaxed while driving long distances, staying alert is equally important. So don't be too finicky behind the wheel. Maintain a relaxed posture but keep your eyes on the road and hands upon the wheel.
It's also a good idea to give your clutch foot a rest while on the long haul, since you don't need to change gears as much. If your car has a dead pedal, use it, otherwise just keep your left foot on the floor board near the clutch pedal.
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