Now you have some angry, unkind, or cranky thoughts—and there’s a consequence. Your brain releases chemicals that cause physical reactions. You may feel your muscles tense, your heart pound, your hands sweat. The body is a receptacle for every negative thought we have, and it reacts to each one.

Imagine the difference if you viewed your day as Melanie does, with a positive take on whatever comes your way. You’d skip all the unpleasant emotions and physical reactions that accompany negative thinking.

Your Thoughts and Your Health

Thoughts can create stress in our life. And it’s been well documented that stress negatively affects health in many ways.

Humor, on the other hand, helps your brain function in a healthy way. In reacting to humor, both sides of the brain are activated simultaneously. When you tell a joke, the left side—the part responsible for thinking—starts firing. When you “get” a joke and start laughing, your right side becomes active.

Research indicates that people tend to be more creative when they see something as funny. Other studies suggest that laughter helps increase the flexibility and creativity of thinking. Humor even has been used to help strengthen the immune system.

Thoughts create emotions that can have a lasting physical effect on your body. For example, when we dwell on old hurts and wounds, we build a mental habit. Every time we think about that pain from the past, stress—and its toxic effects—surfaces with increasing speed. Each time we think that negative thought, we build a stronger pathway to that negative emotion, and we’re more likely to express ourselves in a negative way.

Our emotional pain can even trigger physical pain or damage. Researchers have linked toxic thoughts to heart and vascular problems, gastrointestinal problems, headaches, skin conditions, intestinal tract disorders, chronic pain, lung and breathing disorders, and immune impairment.

Consider this, from Dr. Caroline Leaf’s Who Switched Off My Brain?:

Research shows that around 87% of illnesses can be attributed to our thought life, and approximately 13% to diet, genetics and environment. Studies conclusively link more chronic diseases (also known as lifestyle diseases) to an epidemic of toxic emotions in our culture. These toxic emotions can cause migraines, hypertension, strokes, cancer, skin problems, diabetes, infections and allergies, just to name a few.

As a negative thought begins to develop, it activates a section of the brain that releases emotions related to the thought. If it’s a negative—or toxic—thought, one of those insidious “downer” chemicals is released, stimulating the release of another, which stimulates the release of yet another.

Chemicals released by negative emotions can affect your brain’s nerve cells, causing difficulty in retrieving memories. That, in turn, suppresses the ability to remember and think in a constructive way. Chemicals released in the brain as a result of positive thoughts don’t cause this kind of damage, research shows.

Toxic thoughts impact both emotional and physical balance. The hormones released can disrupt positive brain functioning, making it difficult for us to concentrate or focus.

The good news is that our thoughts also can create a calmness that helps control our emotions, reining them in before they spin out of control. Every positive or happy thought spurs your brain to action, releasing chemicals that make your body feel good.

Why Self-Talk Matters

This is where the power of self-talk is so evident. Self-talk is simply the thoughts you tell yourself. For example, Melanie may step out of the house, notice it’s raining, and think, “Great, the yard needed some water.” On the other hand, her friend Rhonda, who feeds herself a steady diet of negative self-talk, would probably think, “Oh, rats! Now I’ll get my hair and shoes wet. And it will be rough driving in to work. And I’ll probably catch a cold. And...” You get the picture.