Right. They have to realize they are failing as a person too. That's where friends and family come in and say hey, "You may not like it but this is tough love , and you have a serious lying problem that has got to be attended to". goodluck. I try not wasting any time on liars. They have to accept responsibility.
I don't think you really can stop one from lying because it is part of the person's make up. Some are so convincing lyers too!!!! I believe it is a form of expression that, for some, shows superiority in knowledge, a need to feel intelligent. Some actually believe they are telling the truth, mental issues..and some just being stubborn. I'm not ruling out lying can't be cured with professional help, but the person has to know help is needed and wants to be cured.
Joke around tell them that they don't need to lie you'll still be freinds let them now how good or bad it is they can trust you. It's them trying to look better or feel better about theirselves help them stop