Why, instead, do you shut them in a dark room, alone with a stranger, to talk about things that make them sad?
FWIW, this isn't really how therapy goes. At least from my CBT experiences, its a few minutes of talking about what we're currently struggling with, then decoding those topics to learn how we distort our experiences and memories towards the negative / stressful.
Then usually the "homework" would be small actionable steps to build up habits to become aware of these distortions, as well as habits to make other healthy choices.
Not discounting Andrew's story one bit, just putting a bit more light on what modern therapy aims towards.