David Montgomery, I shared your marshmallow analogy with a Jesuit mentor/friend. It immediately sent him down memory lane. His reply was this:
Lots and lots of mini-marshmallows. Example: “I had 26 unclean thoughts yesterday and I imagined a swear word in public.”
Apparently every unclean thought was worth a Hail Mary back then. And woe be to the confessor who did not treat each of these sins as deadly serious.