Humans have tens of thousands of thoughts every day (the number is up for debate). Some are helpful, some are unhelpful. An example of a helpful thought is "It's going to rain. I should wear my boots." An example of a potentially-unhelpful thought is: "It's going to rain. I might get in a car wreck now." Healthy, normal people have both helpful and unhelpful thoughts every day. However, a person tends to dip into a full-blown anxiety disorder when they pay too much attention to the unhelpful thoughts. Notice I said "when they pay too much attention to." I didn't say that non-anxious people DON'T have negative thoughts. They do. They just tend to let negative thoughts pass by. They have a better relationship with negative, unhelpful thoughts.
This is why counseling for anxiety is so effective because it teaches anxious people how to retrain their brains and relate to their thoughts differently. For example, counseling might teach you to challenge your negative thoughts in a clever way so the thoughts don't hold so much power over you. The graphic provides a great example of thought challenging based on Mindfulness-Based Cognitive Behavioral Therapy.
Finally, it's important to remember that negative thoughts like "I might get in a wreck" are helpful to a degree. It's these thoughts that help us slow down and turn on our lights during a rain storm. So again, don't poo-poo the negative thoughts. Learn to work with them. An effective therapist can teach you the skills to do just that. If you can learn to control your thoughts, you control your life!