That statement good is better than the best depends on what angle at which you're looking at it. If for instance a second class degree graduate gets a good paying job while a first class degree student is yet to get one several years after school, then that statement holds true.
But I don't believe in that statement though. I think people should strive for excellence and not be content being average or a mediocre at anything in life. Good is not good enough. Life thrives on dynamism. Seek to be better.
A lot of people who were good at certain vocations years back are out of job now because the society has long taken a great walk along the path of progress and these people didn't fit in any longer.
Keep improving your skills, upgrading and updating your knowledge on recent developments around the world. Don't be comfortable settling for less, be the best.