"one reference" - He only spoke about his sadness one time.
"insupportable sadness" - A sadness so deep and strong that you think you won't survive it. You feel as though a knife went through your heart, your spirit is completely crushed.
"won over and over" - You have to earn it or achieve it, and not just one time, but every time you want it. No one is perpetually happy. But you can "win" moments of happiness, such as working hard so that you get a raise in salary at work, or following a diet and losing weight. Little everyday "battles" that you can conquer and make yourself smile.
Student or Learner