We worry. We watch what we eat. We floss our teeth. We work out and walk four miles a day but only after slathering on SPF-60 sunscreen. We practice tai chi, home-brew kombucha, and monitor our cars and skin for strange noises and morphing moles. We watch our children sleep. We stretch. We stare intently into toilets before flushing them.We do all this because we care about our health, our lives, ourselves. We want to make whatever choices will most likely let us stay with those we love as long as possible. Will folic acid help us do that—or will downward-facing dog?But how much concern is too much? Where should we draw the line between attention and obsession? A soupçon of worry keeps us safe. But can more than a little bit make us sick?Worrying Is WorrisomeRecent studies say yes. One study, published in the British Medical Journal, found that even very low levels of anxiety and “psychological distress” raise the overall mortality risk by 20 percent and the risk of death from cardiovascular disease by a hefty 29 percent. Similarly, a Purdue University-affiliated study found that highly “neurotic” peopl …