All spoken words are like a rocket travelling through space and on its way it releases forces and awakens entities. If you regret having spoken badly about someone, make amends by saying something nice about them.
But hurry, because the more time passes, the less your good words will have the power to neutralize your negative ones: for since you said them later, they have been recorded in a different layer of the atmosphere and the layers are superimposed.
There is a means that is still more powerful than speech: that of thought.
But another problem arises: thought and speech belong to two different planes. Speech belongs to the physical plane, like a wave that moves through the air; while thought belongs to the etheric plane.
But try all the same. If you have unknowingly said some unfair or unkind words about someone, when you realize you have done so, try to connect with the benevolent entities of the invisible world and, by means of thought, send this person much light and love.
Some damage might have already been done and it will take time before they feel the effects of your good thoughts, but you will have avoided the worst.