The most common is to tend to "disappear" by little desire to socialize, fear of hurting, "shit", not wanting "nothing", to show fragility, fear that certain people can hurt you to be more prone to subsidence by a minimum comment, etc. The truth is that who suffers in the third person, it is difficult to understand and, until looking for a reason (sometimes, can be founded) also costs in better stages. But the body does not ask you to want to show yourself in those times and you seclude yourself in your own prison of pain and loneliness. We all know that it is very pernicious.
Unfortunately self-destruction is like that but despite this, we have to fight it and talk, externalize what you can with the people closest to you (as much as possible, giving you courage and with very close people who can understand you) because it helps you to vent and not lock yourself up, and not for that, you will make others around you suffer more, just the opposite, making them worry even more.