What happens if you lie so much?

In general, if you tell a lie or misconstrue a statement, you are generally filled with a sense of guilt. When guilt builds up (perhaps through repetitive lying?) it causes the person to feel bad about themselves, and in certain cases will affect general behavior e.g. sleeping, eating, general washing and cleaning etc.

This is only in general, for some people, they could lie for the rest of their lives and think nothing of it. It's always best to tell the truth, but can be necessary to lie.