Applejack has depth that a lot of people fail to recognize. She struggles internally trying to figure out what the appropriate depth of her honesty should surface as in reality and she often times feels she's been disingenuousness for withholding these truths from her friends & others. It weighs on her and she wonders if it's just polite disclosed nitpicking, or repressed psychotic disgust.
Applejack is a perfectionist and she has a very important job, they basically supply a mass with a large portion of their diet, across the board. The Apples are wealthy in value when you take what it considers to spend on the upkeep of hundreds of acres of apple trees, a farm with livestock, a 3 story home and all 4 apples that live in it.
I think sometimes she feels like she's lost in the motion of things and feels mechanical, but since overcoming the loss of her parents at a young age, stepping up and embracing responsibility felt like an objective inevitability for her and some times, maybe she "cries on the inside", from a missing childhood, and involuntary parental detachment, replaced by hard labor & endless responsibility.
Ultimately she enjoys this "mechanical existence" and it's in her nature to complete things, finish tasks, fix things, and help others because without these things to do her existence feels hollowed out and empty, she wants to take great pride knowing how her parents would feel about how she's stepped up to the plate, so she is internally neurotic about such things.