It's the old catch 22, you can't make the guy aware so he actually understands or knows what he is doing wrong. With smarter/more aware students, they can understand and eventually correct what they are doing wrong (if you explain and understand it well enough yourself), even if they totally screw it up at first. When the student doesn't/can't, it's the source of much frustration and long hours. Sometimes they eventually get it, sometimes as you say, the end is simply not in sight. Don't want to sound mean, but it's exactly the problem of someone that is "too stupid to know they are stupid", or "not smart enough to know they are not smart", maybe as a better way of putting it.