For out of the abundance of the heart the mouth speaks. – Matthew 12:34
The best metaphor for this that I know is that if all you eat is potato chips and ice cream then you’re never going to get the important nutrients that your body needs. Your body needs vitamins, potassium, calcium and magnesium in order to be its best. We’ve all heard the saying “You only get out of it, What you put in” ; well if all you eat is fatty, junk food then your results will be laziness and fat. This saying can also be applied to our spiritual lives. If you fill your heart and mind with bad things then your actions will reflect that. But if you fill your heart and mind with the good things, the things God wants of us, then you actions will show that.