"Out of the overflow of the heart the mouth speaks.'

If you squeeze a tube of toothpaste, what comes out of it? Toothpaste, right? What about if you squeeze it as hard as you can, or stamp on it with your foot? What comes out then? Manure? No, more toothpaste! Well, so it is with the human heart. The amount of pressure makes no difference to the content of what comes out, only the amount. The principle remains the same: Pressure makes what's inside come outside. The question for you and me this morning is quite simply: when life (or people) squeezes your heart, what comes out, and why?

We could drive this illustration in a thousand different directions. Let me choose one: Be careful with what you fill your heart. How does a person become discouraged? They fill their heart with discouraging thoughts— discouraging thoughts in response to difficulty. How does a person become bitter? By filling their heart with bitter, resentful, spiteful thoughts. By tending to view the actions of others in the worst possible light. Eor, the beloved donkey in Winnie the Pooh, becomes what he says, and he says what he thinks.

Take a moment throughout the day and reflect upon your mental hygiene. Are your thoughts true (or false), honorable (or rude), right (or wrong), pure (or disgusting), lovely (or ugly), worthy of praise (would others praise you for thinking this way, or would they raise an eyebrow), excellent (or middling, or even worse)? Not all of these thoughts, however, come from us; other forces are at work. People can influence the way we think (for better, like the father in Proverbs 1:8, or for the worse, like the enticing camaraderie of foolish friends in Proverbs 1:10, or the adulterous whore in Proverbs 7:5). The world can affect the way we think (1John2:15-17), and Satan can also influence the going on inside our minds (John 13:2).

Listen to the way you think. Guard your hearts and minds—if you want to live forever, that is (Proverbs 4:23). You can choose how to think, what to think, and when to think it. You are response-able. You don't have to give your mind free reign. Wise men learn to control their tongue (Proverbs 13:3), but they first learn to control their mind (2Corinthians 10:5). 

Watch your engagement with media and music. The images we watch, the movies we stream, the music we play in the background, all powerfully affect the content of our hearts. As Alistair Begg likes to remind his congregation, "Garbage in, garbage out!” And as I tell my children, cultures always sing about their treasure. Listen to the lyrics of the songs on your playlist—what treasure are they singing about? Is it good, beautiful, and true?

The reverse is also true: Fill your heart with Scripture and wonderful things begin to happen:

“I have stored up your word in my heart, _that_ I might not sin against you.” (Psalm 119:11, ESV)
 
“This Book of the Law shall not depart from your mouth, but you shall meditate on it day and night, _so that you may be careful to do according to all that is written in it._ For then you will make your way prosperous, and then you will have good success.” (Joshua 1:8, ESV)

Do you see the principle working out here? What fills our heart really does control the trajectory of your life? The credit card companies want to know, 'What's in your wallet?” God has a deeper question for you: if you are willing to take a moment and listen to yourself think.