It isn't quite that dramatic. When you are driving, I doubt you hover over the brake pedal, in case you need to slow or stop. No need to hover over the juice pedal at all times either. The important thing is to ingrain the thought of hitting the juice pedal so it is a reflex action like hitting the brakes or letting off the juice pedal when you want to slow or stop.
Likewise; I hate to be the bearer of bad news but this autonomous emergency braking is always watching, whether cruise control is engaged or not. The one time I'm pretty sure it saved a fender bender for me was when I was going slowly, with no cruise of any type engaged.