Whether it’s improving our day-to-day lives or surviving a sudden calamity, there’s no substitute for clear-headed mental discipline. And a growing number of people believe they know how to find it. Allan Lokos and his wife, Susannah, were on vacation when their plane crash-landed in the Southeast Asian nation of Myanmar on Christmas Day 2012. “By the time we hit the ground — and we hit the ground pretty heavily — the plane spun around,…