“Just as a stream flows smoothly as long as it encounters no obstruction, so the nature of man and animal is such that we never really notice or become conscious of what is agreeable to our will; if we are to notice something, our will has to have been thwarted, has to have experienced a shock of some kind. On the other hand, all that opposes, frustrates and resists our will, that is to say all that is unpleasant and painful, impresses itself upon us instantly, directly and with great clarity. Just as we are conscious not of the healthiness of our whole body but only the little place where the shoe pinches, so we think not of the totality of our successful activities but of some insignificant trifle or other which continues to vex us.”