Noone's experience could be compared to another one's experience. That is the fundamental origin of the impostor syndrom. Each developer goes his own way towards what he tends to become, and if some paths are identical, we cannot conclude to similar experiences if we take into account qualia.
Qualia are defined to be individual instances of subjective, conscious experience.
That means that if you get an advice, you have to transpose that advice into your own inherent experience before building some kind of experience about it.
Examples of Advice
For me, work hard means read and practice a lot. I need to confront what I understand from a theory with a concrete example that I can manipulate.
That will not be necessarly the same for another person.
Understand What You Are Doing
How do you know my understanding is the same your understanding? I could paraphrase and try to explain what I understood. But there will never be an assurance that I understood what you try to explain to me.
On the other hand, some genius people are capable of doing things they do not understand theorically speaking. And that is not necessarily a problem.
We can sum this up by saying that you may try to be able to reproduce what you did in some other similar contexts, and that might be enough to validate that advice.
I need to understand what I am doing, this brings me confidence. Otherwise, I quickly become stressed and question my whole life and all my choices. That's why I hunt dogmas by trying to explain everything.
But I can beleive that is not the case for everyone. That someone else can live a long and happy life believing something without ever having to confront reason, experience or theory. And it's not necessarily a problem to be able to do something (it could be a problem if you have to teach someone).
What Is it Like to Be a Developer?
To be a good developer, you should seek to feel positive things when you do what it is for you to be a developer. That is, in the end, the only thing that matters.
And, please, forget comparisons, competitions. Help your entourage by listening to their questions, after all, it is the rubber duck technique that works so often in our profession.