The baby is bitter in his heart, and no one can understand the next sentence unless the baby says it. This sentence is usually used to describe a person's inner confusion, dissatisfaction or frustration, but he is unwilling or unable to express it, suggesting that the other person can't convey his inner pain to others through words or expressions, and feels misunderstood or incomprehensible by others. So in real life, when a person feels troubled, painful or unbalanced, sometimes they may choose to keep silent and don't want to speak out or ask for help. This may be because they are afraid of being laughed at by others, don't understand, hurt or worry about bringing a burden to the people around them.