Because we must be weak to be strong. All that we go through determines our strength and those who are the strongest do not have the easiest past. They did not take the smooth paved road, they took the rocky one.
Fun Psychology facts here! You mean to tell me you think this fact is FUN? Nothing about depression is fun. Not a single angle of it. Even if that was on psychological things, and not depression. It shouldn't be marked as a FUN fact.