To use manners it is free.
It's the nicest way to be.
It does not hurt to be kind.
Other's being good back is good for the mind.
If you're saying something harsh that needs to be said, use self-control.
You will find this is good for your soul.
It doesn't hurt in this instance to talk euphemistically & use diplomacy & tact.
This costs nothing but a bit of thought & that's a fact.