I'm a secondary teacher and students who lack resilience are a big issue. The whole growth mindset thing is an attempt to deal with that. A lot of it is about avoiding ego involvement in learning, as this can be a barrier.
For example, we get lots of bright students at A-level who have coasted at GCSE. They've always been told they're smart, been on the G&T register (the term G&T makes me grit my teeth), and received lots of recognition for their innate intelligence. They come to think of that intelligence as being a key part of their identity, and actively avoid challenge because any perceived 'failure' on their part would be a blow to their ego and damage their self-worth. These students almost invariably don't achieve their potential at A-Level.
I've taught a lot of students who won't revise for their exams. Generally it's due to this: if they fail, but haven't revised, they can still tell themselves they're smart and would have got an A* if they had chosen to try. The thought of effort followed by failure is terrifying to them. They're not lazy or thick - they just lack resilience.
The opposite, of course, are students who actively seek out their weaknesses and aim to address them. They're disappointed by failure (and by 'failure' I don't, of course, mean abject failure - just a low mark on an essay or whatever) but not put off by it. They work hard even when the going is tough. These students frequently (usually?) overtake their 'more able' peers.
I quite like the 'pit' metaphor - sometimes being stuck does feel like being in a pit, although I don't know if that's more true for older students when the stakes are higher. In exam season students cry, and stress, and work late into the night, but if their hard work results in success they can be really proud of then it's worth it in the end. Calling it 'the pit' is recognition that learning isn't always happy-clappy fun time - learning is hard, and sometimes lonely and miserable, but we've all been there (I remember long, desperate nights at university when I felt like the only person awake in the world) and we get it. Just because you're in the 'the pit' doesn't mean you're stuck in there on your own though - there are people to help you pull yourself out.
Interestingly, I once did a questionnaire on growth mindset with a group of Y8s (not my own class). The only student who thought his intelligence was fixed and that he would never get better had quite severe SEN. Really sad.