It takes 14 truths to make up for one non-truth. That's what I remember being told as a kid. Don't know why they use that exact number - that's not the point - but the concept rings true, regardless. No matter how many truths you've ever told, one non-truth can bring u down. Way down.
On the other hand, some people find that they overrate themselves. In that case, it is said, that one who does that, will not leave this world before achieving that which he aspires to achieve. This might be difficult to understand... Basically let's say that someone decided to pretend his new life away, that he was a millionare. Well, he finally would one day become one because he'd have to prove his assets. Whatever, it's a lame example. Anyone have anything better, feel free...

Another thing, sometimes we convince ourselves of something. We can get so caught up in the action, in the stories we tell - and okay I'll speak for myself - sometimes it becomes difficult to see the difference between reality and exaggeration. When it hits you the hardest is when you realize that the one security you had, the one person you trusted with your mind, emotion, spirit, and heart, has blurred this vision of conception. It is then that you begin doubting yourself - your judgment, your aggression, and your emotions.