Why does Jessie want to kill herself?

Jessie suffers from epilepsy, which she blames for all of the things in her life that have gone wrong. Based upon Jessie's experiences, we cannot really say she's wrong. Her husband left her, her son is walking the wrong path, and she cannot hold a job. Seizures have interrupted and affected her life at every turn. Thus, Jessie, who feels like she's never been in charge of anything, decides she wants complete control over the manner of her death..... suicide.