Physical neglect eventually becomes mental distraction.

Physical trouble does not stay in its own department. Poor sleep, constant discomfort, low fitness, and an unaddressed ache all end up occupying the mind, showing up as irritability, poor concentration, or a low-grade sense that something is wrong. The mental symptom often has a physical cause that nobody looked for.

When your thinking has been foggy or your mood flat, check the physical basics before analysing anything. Sleep, movement, food, water. It is unglamorous and it is frequently the answer.