the little engine that was filled with existential angst

Once there existed for the purpose of analogy a steep hill up which a train track ran. It was very steep; observing it one might have questions whether the trains could reach the top.

The first train to attempt the ascent might have questioned whether it could reach the top, but it lacked the mental capacity to do anything other than what it was designed to do. There was no "I think I can" as it mounted the peak; it merely did, and did well, and that was all that was important to it. That was also all that was important to its masters.

The second train to attempt the ascent lacked a sense of duty; when it doubted whether it could drag its load to the top of the hill, it merely abandoned its load on the tracks and continued on its way. This saved it a lot of time and effort, and freed it from the heavy burden of doing someone else's labour.

The third train to attempt the ascent attempted to drag the abandoned cargo as well as its own to the peak. It failed in this attempt, and rolled back down the hill, applying its brakes the entire way so that when it reached the bottom it would not continue going anywhere. It stayed there, dejected at its inability to actually make a difference.

The fourth train did not even attempt the ascent. When it saw the abandoned cargo and the train that was unmoving, it despaired of any attempt and immediately gave up, heading the other direction to report its failure.

The last train to attempt the crossing, while disheartened by the evidence of failure, did not give up there; it instead attempted the crossing. "I think, therefore I am," it repeated to itself, uncertainly, as suddenly it began to experience dread. It knew that it could make the decision to climb or not to climb, to surrender or to be like the first train, and that its decision would shape the course of its future. It found itself wondering what the purpose was of the hill, of the cargo, even of the track, whether it was the pawn in some greater scheme or whether it was alone in a great dark expanse of universe--whether this hill was a trial made to test it or whether it was all without meaning and all full of despair and hopelessness. As it crossed over the hill, it learned an important lesson: it's always easiest to continue what you are doing, because that generally doesn't involve making a choice.