When I'm looking for good phrases to tell to my kids, they have to be short and meaningful, and if they rhyme, it's a huge bonus. "Smart's a good start" is one of my favorites because it captures much of what I feel was missing from the teachings of my childhood, and provides through ambiguity the potential obvious solution to the real problem I've seen since then.
Growing up in the 80s, I was part of the "latchkey" generation. My parents had been raised by WWII survivors and were now raising children of their own. They had been told during their childhood that "children should be seen and not heard" and that they should be happy with what they had, because it could be so much worse.
This pendulum swung pretty hard back in the other direction. The information boom was paired up with the free love philosophies of the 60s and 70s and the reigning recommendation was to remind your children how smart they are, how wonderful they are, and that they can do anything. With this backdrop I, and most of my friends in suburban America, lived out my childhood. We were all smart, all special, and all could do anything we wanted. It's unsurprising that the real world gave us quite a bit of trouble when we realized that we're not more special than others, we're not able to do anything we want, and that while hard work pays off, smart is only a good start.
Smart is a binary test: either you are or you aren't. I was a mediocre student. I saw little value in school, and less value in applying myself. If I didn't do well on a test, my sense of self as a smart person was wrong. If I did well, it was proof everyone was right, and I really was smart.
Ultimately I reevaluated my worth based on trait other than smartness, and found value in working hard on things I'm passionate about. I'm optimistic that my kids will realize that they can be anything or do anything, but most things take effort, and the effort is what's valuable.