When you lie you must keep it going by continuing to lie.
When you lie you must keep it going by continuing to lie, that's the only way the first lie you tell is relevant. So with knowing this, why do people continue to lie?
Some people think they are so good at lying that its not a problem, but to someone that catches you in that lie you never can gain their trust again. Not only do you loose their trust you also make a fool of yourself. Lying is a technique, you should know where and who to lie to depending on the situation.