talk when you are really heard...

वचस्तत्र प्रयोक्तव्यं यत्रोक्तंलभते फलम्।

स्थायी भवति चाऽत्यन्तं रागः शुक्लपटे यथा॥ ३४

पञ्चतन्त्रे मित्रभेदे--

vacastatra prayoktavyam yatroktam labhate phalam|

sthāyī bhavati cā'tyantam rāgaḥ śuklapaṭe yathā|| 34

pañcatantre mitrabhede--

Good words should be uttered only where such words bring good results..

Words so uttered become long lasting and useful till the end, just like dyestuff applied to clothes of bright white colour.

And when we apply black dye on a black cloth , that will make no impact..

वचः words तत्र एव in those places alone प्रयोक्तव्यं should be uttered, used यत्र where फलं लभते. gives result 

तद् प्रकारं like that उक्तं वचः world told शुक्लपटे on white cloth यथा as रागः permanent dye अत्यन्तं स्थायी permanent भवति च happens too.