Why am I so Anxious?
The quick answer to your question is that your anxiety point to problems with your autonomic nervous system (ANS). A more detailed answer requires some delving into the way memories, emotions and the body interconnect.
The ANS is responsible for actions outside of your conscious control, such as your heartbeat, but it also comprises a system to help galvanize you into action when required and another to help settle you down. It helps therefore to know a little about why things go wrong with the ANS.
One reason your body swings into action is when you feel threatened. Indeed you are fully equipped to sprint and take cover from a predator, a falling tree or maybe a fire; not so useful these days but still handy for dodging traffic or slamming on the brakes! And you've felt it, that moment of heart-stopping (actually heart racing) anxiety. Inside, your body is releasing a cascade of stress hormones which then can hang around for hours after the threat has past. A thousand or so years ago your moment of stress would slowly give way to a state of calm and relaxation. Today this simple on-off relationship has given way to ‘mainly on' and ‘rarely off.' Your ‘on' system dominates your ‘off' system because you're designed to survive. This means even though you think you're relaxed, a part of you remains watchful and vigilant.
The reason why you feel anxious also has something to do with your emotional memories. Strong negative emotions such as fear and disgust are tucked away into your unconscious mind, just waiting for the right moment to stir things up. These memories are stored in an area of your brain associated with your fear response. When you feel anxious it's probably very frustrating. This is because at a conscious level you know your feelings bear little relationship to what is happening around you. At an unconscious level those malign memories interact with what should probably be a rather modest state of arousal and generate anxiety. You, meanwhile, are left scratching your head over the irrational and illogical sensations you are experiencing.
In some people just the flow of stress hormones is enough to activate the area of the brain responsible for fear. What's worse is the fact that this can happen if they are hungry, thirsty, or maybe if they've picked up a virus. You perhaps don't think of hunger or thirst as stressors but to the body these are signals that things are depleting. In turn it releases hormones to encourage you to fix the situation. Unfortunately these hormones can act to switch on the fear center in the brain. If this occurs, the brain will send and receive fear signals, which if prolonged and intense can cause panic attacks and lead to chronic anxiety.
One of the reasons therapists try to uncover core beliefs underpinning anxiety is an attempt to access and then recast implicit memories stored within the fear centre of the brain. If the anxious person can redevelop such memories it is a huge step in the direction for resolving or coping better with anxiety.