One thing I like about travel, that is perhaps only tangentially related to travel itself is that it stops me from becoming lethargic, even in pure leisure.

At home I tend to fall into bad, unspecified, habits, lazyness and a general, not exactly malaise since it's not unhappy, but just a nothingness of regular life.

And I have to try to prevent myself from falling into that.

Not so during travel. Without needing any concentration, willpower, or even much decisiveness, it is its own motor.