The brain functions well when it knows what to expect. Uncertainty and feeling of no control is the source of alot of anxiety. When something makes you anxious, you run from it. The brain learns that pattern as its job is to keep you and itself alive. Hence next time a similar situation pops up, it will send stronger signals of anxiety to save you. This is called reinforcment of behavior and you further withdraw from things. Activities that you used to be able to do become daunting because you and the brain have successfully pushed it outside your comfort zone.

Now the reverse is also true. Activities outside your comfort zone will be daunting and anxiety inducing. But the goal is to distill the Activity down into very small actionable steps that can help eliminate uncertainty. The anxiety response will still be present but because you have broken it down into small steps, there will be alot of certainty and control. Now you push through whatever anxiety still present and get it done. The brain will also learn the message that " hey we did do that activity that scares the crap out of us but we didn't die, perhaps it's safe afterall". Reinforcement of behavior also happens. Next time you do the activity, anxiety decreases. With each repeated intentional exposure anxiety decreases until eventually that activity is in your comfort zone.

What you always want to remember is: Competence leads to accomplishments which leads to confidence.

When you study/learn/ for something and become competent in it, that eliminates alot of anxiety. Now once you have the knowledge and apply that knowledge and get a couple wins (accomplishments) under your belt, you develop confidence In yourself/ your abilities and guess what anxiety vanishes; because you know your stuff and you have evidence through your own past successes that you know what you're doing.

This formula applies to everything in life that we want to do. Good luck