Failure to study the laws of loshon hora can result in a person’s speaking loshon hora frequently, without even realizing it.  The following true anecdote illustrates this point:

Someone asked a certain woman if she wished to borrow a copy of Guard Your Tongue to study the laws of loshon hora. Her reply was: “I don’t need it.  I never speak loshon hora. But my husband really needs it.  He always speaks loshon hora about others.” ~ R’ Zelig Pliskin