I think the advice here is "get as good as you can, get as smart as you can, and then, when you decide to set off on embarking on a calculated risk, try to forget all the noise around you and stay the course."

I feel like the problem is there's a lot of wannabes who skip the steps of actually gaining competence and then disregard the advice of others. That's not going to work. The first step is years of hard work. For instance, crank physicists who don't really understand graduate level physicists are not going to accomplish anything by disregarding the advice of others.

However, if you know what you're doing, don't second guess yourself when embarking down a risky path. It's probably not as dangerous as it may seem.