When a person is angry with another person, that person is removed from their heart. That's why the physical reaction is to shout. The greater the distance, the louder the shouting. But when individuals are in love, they speak softly, and when they are further in love, no words are needed.
Prayer may take the shape of sacrifice, supplication, adoration or meditation; it may even appear in simple daily acts of kindness; but it is always the outer visible sign of an inward communion with the Divine.