I think CBT works well for acute mental illness but not necessarily for chronic, severe mental illnesses such as bipolar disorder. I believe this is especially true when one is symptomatic. When getting out of bed is a challenge nobody is going to get me to do my CBT homework.

That said, when I have been stable and able to concentrate on the exercises found in one of my books (yes, I have 3) I have found CBT helpful. It builds skills that I can draw upon when I am having an episode. While it may not prevent the episode, it makes going through it more manageable for me.

Good luck on your CBT journey.