When you can’t fall asleep because you’re too stressed , counting sheep might not be enough. Instead, experts suggest a simple mental trick that can quiet even the busiest thoughts. They know because they use it themselves. The technique is called “cognitive shuffling,” and it’s a mental exercise that gives your brain something neutral and mildly engaging to focus on, so it can drift toward sleep instead of churning. Here’s what to know—and how to tell if it might work for you. What is cognitive shuffling? The concept was introduced more than a decade ago by Dr. Luc Beaudoin, a cognitive scientist, who was initially inspired by his own struggles with insomnia . Here’s how it works: Once you go to bed—following your normal routine—pick a word that doesn’t carry much meaning to you and is five to 12 letters long. “The word should be emotionally neutral, so not something tied to stress or strong feelings,” says Patricia B.…