From what I've seen on the subject, the emphasis is on B and C, though they don't spend words on avoiding A.

CBT is just a way to steer your thoughts, and is the same thing aspiring rationalists would do when they catch themselves counting sunk costs.

Using CBT to fight depression is almost certainly instrumentally rational, and most likely epistemically rational as well, but if you hand someone a steering wheel with no instruction on rationality, there's no guarantee they'll beat the autopilot.