The reality is very different. They are expected to achieve in school work, in exams, in interviews, in job applications. They are expected to be popular, socially competent, able to make friends. There are external insecurities, shifts and changes. Families move house - and children lose familiar social and school structures.
Parents get ill, separate, divorce, die.
There are internal insecurities. Not feeling bright enough, not feeling attractive enough, not feeling sexual enough quite simply, not feeling good enough. All these problems may then be heightened and exacerbated by isolation. And then you have no one to help you take the strain. After that, it is an easy step to mental upset.