I strongly disagree with this based on personal experience. I regularly met people I was smarter than in medical school who _consistently_ out performed me. And the reason was simple: They were _extremely_ diligent, hard-working, motivated, and professional. Among other valuable lessons I learned that people vastly overestimate the role of intelligence in just about every aspect of life. It can give you sorts of advantages in life, but the majority of success is still chalked up to grit, persistence, motivation -- and the knowledge that results from it.