I came here to say this, and also to say that nursing closes some doors, but it opens up others. Doctors I know often regret not becoming Nurse Practitioners, who can do almost everything doctors can do, but also get to switch fields when they want to, and get paid pretty well too.

Still, that's about the details, and your post is about the generalizations from them. I think they're pretty interesting generalizations, but mostly I just want to point people reading this to Study Hacks for a lot more conversation about how to achieve excellence in whatever field you end up in.