How to deal with someone who says one thing and does another

1. What do you call a person who says one thing and does another thing?
2. Why do people say one thing and do the other?

What do you call a person who says one thing and does another thing?

A hypocrite preaches one thing, and does another.

Why do people say one thing and do the other?

When actions, thoughts and words are disconnected, a person lacks congruency. They end up out of sync and lacking in self-awareness. They do something because maybe it feels good in that moment and seems like a very good idea.