In plain words
One must strive to purify the Manas and speech
The Upaniṣads have gone on teaching the disciplines that check the conversations in the mind. The very first discipline is prāṇāyāma. Prāṇāyāma is not a gymnastic exercise, nor a fearsome discipline. Drawing in the breath is pūraka. Letting out the breath is recaka. Holding the breath between these two is kumbhaka. The Manas must be made one-pointed during this pūraka, recaka and kumbhaka. When one asks in the Manas, “Who is going in? Who is going out?” the conversations in the mind dwindle away. If the Manas is set on watching the in-breath and out-breath in this way, strength of mind is gained.