【正确答案】It is a common saying that we do not fully learn the value of a thing until we lose it. We often treasure the love offered by our friend when he has been taken from us by death, more than when he was with us in the flesh; it is only when we have left school or college that we understand the greatness of our opportunity of education, which has gone forever; and it is the weak and the sick who realize the value of good health.