I agree that generally we don't go around saying to ourselves that we aren't going to kill anyone next Friday because as you say that lies outside of common or normal behaviour. But presumably if you were a serial killler trying to stop you would do just that!
The way I drank wasn't normal behaviour and I need a way in which I can be consciously sure that I won't be drinking next Friday. For me, this is both the realisation that I can stop if I really want to and that I have a sure fire way to stop: to just allow any AV to rise and fall without me getting caught up in it. Both elements involved some faith or trust for me to give it a go but as you say it may be different for others, When I found it worked that trust became internalised and no more conscious than the trust I have that other drivers will drive responsibly whenever I get in my car.