Combine discussion of “Explanatory Style: Optimistic/Depressive” with the phenomenon known as the vicious cycle of depression. [Both of these are discussed at length in your text (Ch. 12).]
Feel free to use an example, such as being laid-off from a job, having someone break up with you in a relationship, etc. in your discussion, if it makes it easier to explain.
Text : Social Psychology (13th Ed.) David G. Myers, Jean Twenge