That said, I did realize much latter on all of the inner workings that come to play regarding mental inertia, for again I always look for mechanical interpretations:

Yes, inertia is inevitable. It's a fundamental primitive survival mode which the brain will always strive to achieve, because in the beginning, anything you were doing repetitively better be to keep you alive, so by recognizing repetitive patterns the brain can replace costly and slow conscious computation with fast and cheap mindless repetition (of a task that's supposedly essential and that's why you are doing it), increasing your chances of survival. Of course the brain do not interprets "essential" from "non-essential", but that way of operate was, for our ancestors, completely compatible with those definitions, and that's the reason they survived, and that's the reason those are the genes that were passed on. We are still chimps living in a world that haves evolved much faster than we can adapt.

That of course couples with our ability to adapt to changing conditions, but still the brain will look for unchanging conditions, being naturally averse to change, for if you were alive before the change, by default change means decreasing chances of being alive (in the same sense that "a sound in the bushes is something that will kill me, don't stop to check, run right f now or you are dead").

Due to that, shifting always implies strength, cant be something natural, must be enforced. Thus the phrase of Picasso: "just, start".