E. L. Konigsburg's The View from Saturday is a story in which a teacher challenges students to be more than they are and more than they are expected to be. At one point in the text, a student is "heard" saying that "sometimes silence is a habit that hurts." This quote comes from part of a larger internal conversation about what should have happened in the student's life.
"I never told Nadia how much I liked seeing the halo the sunlight made of her hair. Sometimes silence is a habit that hurts."
In context, the quote opens itself up to new light. The quote refers to the idea that is very important to tell others how we feel. We should not wait for the right moment, for that "right" moment may never come. Instead, we should seize every moment as if it is our last. Essentially, the student is stating that it hurts to not say something when one really needs to (since it may weigh very heavy on one's heart--make them feel it very deeply).