In my opinion, the line often crosses where a person can already choose, but does not want to. I remember how an acquaintance drank every night "due to stress" and then excused himself that it was an illness. The father in the church told us simply - if you can stop for fasting, then it is not just an illness. And what do you think, where exactly is this border?
I agree with you, Boris. My husband, God forgive him, also made excuses for "nerves" until he stopped for Lent one year - then he realized he could. In my opinion, the limit is where a person already lies to himself and to God. What do you think, did your father say anything else about it?