Speech carries enormous power. Krishna defines its austerity with four qualities: words should not cause distress to anyone. They should be truthful. They should be pleasant. And they should be beneficial. Added to this is svadhyaya — regular self-study of scripture.
Notice how all four qualities must coexist. Truth can sometimes be harsh, so it must be spoken pleasantly. Pleasant words are not always helpful, so benefit must take priority. And above everything, words should never agitate or wound another person.
Grandparents who read the Ramayana aloud each evening, who speak gently to children, who choose their words with care — they practice vangmaya-tapas naturally. Sweet speech and regular scripture study together form the austerity of the tongue.