Speak like G‑d.
G‑d's words are packets of divine energy, articulations of His essence and being.
You, too, can speak from the essence of your heart.
Words that come from your heart will enter the hearts of others. And once there, they will have their effect.
So that the heart they enter cannot help but be moved.
G‑d spoke and the world came into being.
Speak from your heart and a whole new universe might come to be.
The emphasis of the fragment of the Rebbe is on words. It is he best choice because that is how H' created the world. If we follow H's example our efforts are not lost because we offer knowledge, or support, to other people if it is done with with Derech Eretz.
Not told here, but is part of that advice : no lashon harah= don't gossip, and hang the phone if somebody ends doing that. Gossips stains us !
In the same way that we explain to children with kindness, it is how we should do it with adults, yet, not patronizing because you think you know better. That has happened to me when people have to show off that they know better, and demean without thinking the other person even if correct in content. That stance will not get into my heart at all.
If we do what he Rebbe advices, I am sure we would live in a better world.