F. Scott Fitzgerald's The Crack-Up is (in)famous for its personal revelations and tone, which were considered somewhat indecent at the time of its publishing in 1936.
Fitzgerald begins the essay by establishing a general premise, and one more specific to himself; that life is a process of slow decay, and that he himself will never be as good as he once was. Critics have historically been divided on whether this is a measured and insightful reflection, or a self-serving series of whining complaints. Either way, we can see from the outset that this essay is written in careful, but personal language, and it is made quite apparent that Fitzgerald is writing about himself (he mentions his aspirations as a writer and provides biographical information about himself as a young man). The key personal information here is how he "cracked" - that is, had a mental breakdown.
Fitzgerald intersperses his explanations with dialogue as well as tangents, such as his regrets about not being big enough to play football, or his fondness for Scandinavian women, but these are ultimately contributions to his overall depiction of his solitude and unhealthy frame of mind.
The essay also ends without a real resolution; Fitzgerald essentially concludes with the unhappy attitude that he is broken. In his next essay he even comments on this, and suggests that people are never satisfied with an unhappy ending to a story, and that he was expected to elaborate on how he got better. It is worth noting that this time in his life was characterized by estrangement from his wife, continued alcoholism, and self-deprication.