It is true, but it is also important to remember that mood disorders exist and are real. Some people are stuck in "the bad mood" more than others and they require significantly more effort to make progress in what you describe.

Often trying distanced thinking won't be enough. This is a good "apple a day to keep the doctor away", but it does not make you immune, especially if you are already suffering from a mood disorder (or a related personality disorder, or a lot of other mental problems actually).

I'm not saying, however, that this isn't a good, often necessary, foundation for many (if not all) treatments.