The professor holds up a glass of water and asks students to guess its weight to illustrate how problems that seem small can become overwhelming if dwelled upon for too long. While the weight of the glass did not change, one student said holding it for an hour may cause arm pain, and another suggested holding it all day could lead to numbness and injury. The professor explains that life's problems are similar - they can be managed if thought about briefly but will cause stress and paralysis if fixation continues. The lesson is to "put the glass down" or stop dwelling on problems at the end of each day to start fresh and able to handle challenges.