Let’s talk real about the old self for a minute, the old you, prior to coming to Christ.
Compare your old self to a dead body, a corpse.
Do you believe that a corpse has no power? A dead corpse has enough power to do evil.
If you were to take a rat, a dead rat, and drop it in the middle of a gathering of living individual, sooner or later it would decompose and start emitting a stench, a foul displeasing smell that would just chase people out of the gathering. Any dead and decomposing animal is toxic enough to be destructive to living animals.
So, when we compare our old self to a decomposing body, we can see how careful we are to be around people so not to chase them away from us by any stench of our old self.
How do you know your old self is dead?
“For ye are dead, and your life is hid with Christ in God.” (Colossians 3:3)
“By no means! We are those who have died to sin; how can we live in it any longer?” (Romans 6:2)
“In the same way, count yourselves dead to sin but alive to God in Christ Jesus.” (Romans 6:11)
So can something come out of your mouth and be destructive to someone, rather than instructive and constructive? You bet it can.
However, while the flesh, the dead decomposing flesh wants to keep others away from you with its desires to emit its stench at will, you have the Holy Spirit instructing you and constructing you to emit the fragrance of grace toward all at all times.
“So I say, walk by the Spirit, and you will not gratify the desires of the flesh.” (Galatians 5:16)
“Let no corrupting talk come out of your mouths, but only such as is good for building up, as fits the occasion, that it may give grace to those who hear.” (Ephesians 4:29)
“Therefore consider the members of your earthly body as dead to immorality, impurity, passion, evil desire, and greed, which amounts to idolatry. For it is because of these things that the wrath of God comes upon the sons of disobedience, and in them you also once walked, when you were living in them. But now you also, put them all aside: anger, wrath, malice, slander, and abusive speech from your mouth. Do not lie to one another, since you laid aside the old self with its evil practices, and have put on the new self who is being renewed to a true knowledge according to the image of the One who created him—” (Colossians 3:5-10) Amen.