That's what mindfulness is all about: Paying attention—without judgment—to whatever is happening in the present moment. You can do this by thinking of your mind as an ocean. Just as waves are affected by weather, our emotions can be blown around by the winds of change and circumstance, and our troubled thoughts can create turbulence in our minds. However, if you went below the surface of the ocean, you would find calmer, gentler undulations. You can achieve the same thing with your mind. When you begin to feel anxious, take a moment to feel the breath in your body, preferably breathing down in your belly. Imagine your thoughts as waves; see them rise, linger, and pass. Keep breathing deeply and slowly, and keep watching your thoughts. You'll be able to live in the moment, even when it's difficult and scary, with greater calmness and balance. That is letting things be.
This exercise isn't easy, but the well-being that can come of it is huge. It lets you come to terms with reality—the good, the wonderful, and also the bad and the ugly—without being completely torpedoed by it. This doesn't mean that if your worries turn out to be justified, you'll hurt any less. But it will keep you from losing not only your mind but your common sense, just when you need it most.
Kabat-Zinn is coauthor of The Mindful Way Through Depression: Freeing Yourself from Chronic Unhappiness [Guildford Press].