Those Things Which Proceed out of the Mouth Come Forth from the Heart

"But those things which proceed out of the mouth come forth from the heart; they defile the man. For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies: These are the things which defile a man: but to eat with unwashen hands defileth not a man. Matthew 15:18-20

Here the Lord is explaining that those things which cause us to be unclean or defiled begin first in the mind and proceed out the mouth. We say and do those things which are in our hearts. If evil is in our hearts then we will produce evil and be defiled. This reminds me of having negative intent towards others. Always seeing the bad and assuming that the motives of others are against you. If our hearts are filled with negative thoughts we will be suspicious of others and think that everybody is motivated to do ill towards us. With negative or evil on our hearts we can not see the good in others. It is as if we are blinded by a lie and cannot see the truth.