A decision you can walk back is a preference, and preferences never build a destiny.
A person's force stays split as long as some part of him is still negotiating with the room he is trying to leave. Cutting off the retreat ends that negotiation, and the energy that was leaking into persuasion becomes momentum, because the mind stops pricing options it has already ruled out.
Calling himself clean sets down the weight of another man's refusal, and relief of that size becomes boldness, boldness becomes work in new cities, and repeated work compounds into a reach no argument in one room could have produced. Leave the door cracked and the same argument reopens every week, and the work waiting elsewhere never gets started.