Exactly why any individual chooses one specific way rather than another is not well understood. What you may be describing isn't exactly an upbeat mood --- but a terribly depressed person my appear upbeat as they may feel a sense of relief after having made a firm decision to kill themselves. A sudden improvement in mood in a seriously depressed person, without any obvious reason for it, is a warning sign we should pay attention to. Yes it hurts. And it runs a high risk, as a method, of either a slow and horribly unpleasant death, or of failing but remaining brain-damaged on top of the pre-existing p roblems, which is also awful