Congratulations, but not everybody is capable of reaching that conclusion on their own. Like you said, having good parents is a huge part of it. Good teachers too. But some conditions, like depression, bipolar and others, include low self-esteem or excessive self-blaming as a symptom, which in many cases totally precludes reaching the same conclusion as you unless a grown-up tells the kid that what's going on isn't their fault.

Now, if the grown-ups are actively calling the kid out for behaviors that are the result of an unmanaged condition, the prime example being a kid with ADHD or ADD who has trouble paying attention in class, and especially if they're assigning negative traits to the kid based on those behaviors, such as telling them that they're lazy or antisocial, then they're just making everything a lot worse and that kid is likely to self-blame for years, even after receiving a valid diagnosis.