New science shows that sleep is essential to our mental and physical health — and most of us aren’t getting enough. Jason Karp is a successful hedge-fund manager and restaurateur with a close-knit family and a deep respect for work-life balance. Today, his world is cruising along quite nicely. More than a decade ago, though, he was in near-constant overdrive — and dangerously close to crashing. Karp graduated at the top of his class at Wharton business school. He was the youngest person to make partner in his elite financial firm. He had a great deal of ambition and a nearly unquenchable thirst for knowledge.