We're pretty good at censoring our words (although even that is a practice that's somewhat waning in our culture), but every once in a while a person slips.  Out comes this expletive or nasty thought that surprises everyone around us, including ourselves.  Where did it come from?  Jesus told people that, from the overflow of the heart, the mouth speaks.  You mean those words or those thoughts were really deep down inside?  Yep.  I don't know about you, but my heart is full of all kinds of evil things, and I have to make a conscious decision to feed it stuff to draw it back to God.  The moments when my censor seems to be missing have more to do with how my relationship with the Lord is going than with anything else.  Here are some things that I've found useful for keeping my heart healthy:

• A regular quiet time – Spending time with God draws your heart closer to His.  If you're not spending time with Him on a daily basis, then your heart isn't being drawn to His.
• Uplifting music - I'm not against secular music.  Having said that, my heart is much healthier when I'm pumping it full of uplifting or Christian music.  
• Forgiving others - It sounds simple enough, but when we don't forgive others our hearts become bitter.  Is there someone you need to forgive?  I believe that forgiveness is just as important for you as it is for the person you're forgiving.  
• A solid mind diet – This is kind of like uplifting music.  What are you reading?  What are you watching?  What do you put in your mind?  What you put into your mind directly influences what comes out of it.  
• Choosing to worship - When do you worship?  Is it just on Sunday morning?  Are there other times?  The heart that worships God all day long is a healthy heart.

That was not meant to be an exhaustive list.  How healthy is your heart?  When it overflows through your mouth, what comes out?