I drink basically nothing but diet coke. It's probably my worst habit (and it's facing some stiff competition).

I remember one day a few years ago when I signed up with a new GP and had a basic check up. And I had a resting heart rate of 120bpm. Switched to caffeine-free pretty damn fast after that. The point is: Caffeine-free diet coke with fear of cardiac arrest is still better than Pepsi.