I&#x27;ve definitely noticed this, and the cause was never really a mystery to me. Seems like the brain and nervous system would have evolved to benefit from an optimal balance of intro vs extroverted time spent. During externally oriented times the brain is occupied on a task so it would make sense for any anxiety or fear centers to be engaged. While the brain could best utilize downtime by analyze past mistakes or ruminating on things. The fear mechanisms of the brain i would guess use discomfort and aggitation to help spurr on adaption and problem solving. like a neural network stuck in the training phase, too much time spent worrying inward would distort the system and cause problems