William Cunningham lived a long time ago (1805-1861), but I think he has still some things to tell us today. Cunningham was raised within the Church of Scotland, and was preparing to become a Presbyterian minister when he discovered that he was not a Christian. In one of his later sermons, Cunningham made the following observation about conversion:
It is impossible that such an important change can have taken place upon our moral nature, without attracting our attention, and forcing itself upon our notice … unless a man be conscious of having undergone a great and radical change of moral principle through belief in the Gospel, unless he be conscious that his moral principles are very different now from what they once were, he can hardly have any good grounds for believing that he has repented and been converted.
(‘How to estimate [evaluate/gauge] repentance’, Sermons, p. 34).