The power of speech that Hashem gave us enables us to speak many thousands of words an hour, and each word is like a precious stone with which he will get endless pleasure in the world to come. When a person thinks about this he should be overjoyed and express his overflowing gratitude to Hashem for this amazing gift. Like any valuable gift he should watch over it carefully like a doting parent watches his child and makes sure he does not do anything that might cause him harm. That is the way a person should watch over what comes out of his mouth, that it should not take him to forbidden speech, like the verse states, ‘death and life depend on the tongue’.