A professor holds up a glass of water in class and asks students to guess its weight. When they provide guesses, he notes that the weight hasn't changed but asks what would happen if he held it up for longer periods of time. The students note that his arm would begin to ache and could become numb if held for a full day. The professor explains that life's problems are like holding the glass - they seem manageable at first but can paralyze us if dwelled on for too long. He advises students that it's important to put problems down each night before sleeping in order to wake up fresh and able to handle challenges.