Brooke gives a wonderful explanation of a glass of water and it spilling out everywhere if it is bumped. She explains that the same glass would not spill over if it was empty. The same way our actions and words reflect what is in our hearts. If only evil, bad thoughts, bad words, and ungodly actions are buried in our hearts, then we can't expect anything else to come out, especially at the most trying of times. How necessary it is to plant God's Word in our hearts so that our responses will be in line with His ways.
"The good person out of the good treasure of his heart produces good, and the evil person out of his evil treasure
produces evil, for out of the abundance of the heart his mouth speaks." ~Luke 6:45