Paul did not warn against a sudden turning from the truth, for such never happens.
Repentance is revolutionary, but apostasy is gradual.
Reformation may be radical, but departing from the truth is usually a process of drifting. Two men among my acquaintances cursed every breath right up to the time that they were converted, and have never cursed since. But those men did not learn to curse in an instant. They began by using slang and apparently innocent bywords. There was never a man who used perfectly pure speech until a certain moment, and very profane language from that moment on.