If you work in a middle school or high school environment, you have no doubt encountered your share of students who seem to be downright depressed by the world in which they are living at that stage of their lives. For a decent number of these students, they are not being abused, and they do not want for anything in particular. They just hate the constant need to strive for (and denigrate others for) social status. Or perhaps the hate the constant fear of having to fight somebody- a constant in a lot of middle school environments.
In this kind of case, you are dealing with a person who is immersed in a present fatalistic time perspective, in which the present seems to be all that there is. And in a present like that, the entire notion that things could ever get much better seems like some kind of a teasing pipe dream that is never going to come true. A student of this nature can be called emo and simply dismissed, to either eventually pull out of their funk or continue with it for the rest of their (probably unsuccessful) life. But as a teacher, you do want to do better by the people who are under your charge.
Naturally, you can just tell a student like this that if they give it some time and work their best, things are going to get a whole lot better for them in their lives to come. But of course, there is absolutely no evidence of this which you can point out to them, because it would be easy to disbelieve that your life was ever bad. Ultimately, you may not be able to do much.