Possibly Controversial:

I think it's key to read it a specific (overly charitable?) light.

You kind of have to take for granted that it's good advice in context. Someone is feeling discouraged and incapable facing come significant task and the best advice is to not be distracted by the feelings of incapability but rather persevere.

If you're reading it as statement on the relationship between power and persistence .. um .. you're missing it's point. Whether you agree or think it isn't well communicated is besides the point a little bit.