The furor over "if you like your plan, you can keep it" touches on a deep fear in American life: That your health-care insurance can be taken from you. That fear is so powerful because it happens so often: Almost everyone in the country can lose their health insurance at any time, for all kinds of reasons — and every year, millions do. If you're one of the 149 million people who get health insurance through your employer, you can lose your plan if you get fired, or if the H.R. department decides to change plans, or if you have to move to a branch in another state.