Mental fatigue often reflects fragmented sleep, prolonged screen exposure, stress, and constant multitasking. Try structured focus cycles (60–90 minutes work, 5–10 minutes off-screen break with movement and daylight). Support cognition with protein, fiber, and healthy fats; frequent sugary snacks can worsen “brain fog” after a brief lift. Stop late-day caffeine and reduce bright screens before bed. If cognitive fatigue persists for weeks or comes with low mood, snoring/daytime sleepiness, dizziness, or memory issues, consider evaluation for iron/B12 deficiency, thyroid imbalance, sleep disorders, or mental health factors. Seek urgent care for sudden severe headache or new neurologic deficits.