Having been in A-fib several times in my life, if you ever feel like your heart rate isn't steady and isn't changing in the usual way as a result of exertion, GO TO A DOCTOR IMMEDIATELY. Lesson learned. If anyone ever releases a watch that can identify conditions like this with a great deal of specificity and sensitivity, I would consider that far more of a killer app than email notifications on my wrist :).
Health monitoring is going to be incredibly helpful. Beyond just pulse monitoring, I'm looking forward to analyzing trace materials in sweat and the like to notice deficiencies or issues.
Just to be clear - A-Fib needs medical attention, but it probably won't kill you directly.
It's possible to have permanent A-Fib and survive - if not thrive - just fine.
The three things that can kill you indirectly are clots created by blood pooling in the heart, heart exhaustion from tachycardia, and a heart attack from possible ventricular arrhythmia.
I occasionally get A-Fib and it's consistently caused by stress - often lack of sleep (no more all-nighters...) or any situation where I have too much to do and not enough time to do it.
(That thing where people say "Hard work never killed anyone?" 100% wrong.)
Having researched it, the causes are complicated, and stress is only one predictor. There are physiological and genetic predispositions and other possible contributing factors.
So yes - GO TO A DOCTOR. You probably won't die - but you might, and it's very easily avoided.
