There are many situations where you will have to learn how to remain silent. You have to learn how to speak only of what is essential. The level of your achievement and the essence of what you are, are the results of your own speech. Even your illnesses are connected to your speech.
In all spiritual education, speech is taken very much into consideration; correct speech, without any exaggerations. Even a word that is not used correctly can have a serious effect on your consciousness.
Speech is capable of creating a high vibration on your electromagnetic field. Therefore, incorrect speech (criticism, lying, hatred) can create stones in your electromagnetic field.
This is the reason why great teachers advice us to remain silent while we are ill, in order to allow ourselves to heal faster.
Every time you speak about the wrong things you distort the essence of your existence, exactly like someone runs into a concert room and starts banging on a barrel while the rest of the orchestra is playing. Every time you distort your existence, you lack of healthy.