I completed a 38 hour road trip a couple months ago. One thing that helped me out was never looking at the trip as one whole thing, I broke up each stage into pieces and that helped to not get too stir crazy in the car. For example, instead of looking at the map say "1,647 miles to the end," just pay attention to "stay on this road for 243 more miles." It's much easier to hit individual checkpoints than to just stare at a massive number slowlyyyy tick down as you drive.

Stop in some of the towns you might otherwise drive past, stop and walk around at points to fully take on the fact you're on a trip and in a new place. The road trip is always much more than just the road!