I think you need to be somewhat masochistic to do most city jobs - burning the candle at both ends, juggling jammed schedules of meetings, work schmoozing and fitting in friends and family, usually with some added hardcore exercise on top.
So it's no surprise that city folk are pretty prone to 'burning out', extended exhaustion brought on by a combination of stress, lack of sleep and poor nutrition.
Burning out can put people on long term sick leave and be debilitating and career ending, but your body does give you a few hints along the way that you're pushing you're pushing your limits and you need to scale things back, before it gets that far.
For me the first major clue is a sore throat without any other symptoms - so no cold or temperature. My glands in my neck often swell at the same time.
Another clear sign for me is a reduced tolerance to stress - if I find myself getting upset or annoyed more easily or feeling overwhelmed it means I'm overloading my body with stress.
These are both cues that I need to back off from my hectic schedule, get more sleep and make more time to wind down.