Is success more about sanity than smarts?

As we've observed over the past couple of years in a multitude of areas, life is full of peaks and valleys. Successful people, however, always seem to endure the valleys and humble themselves in the peaks. Is this a unwritten secret of success: the ability to stay sane? JC and B-Mic Roc OD on if sanity, not necessarily intellect, is more conducive to success.