Write what you're anxious about down, and then rationalize it on paper.
A lot of times, your thoughts get so jumbled in your head that trying to sort out what you need to do in your head makes you even more anxious. Write it out, read it over, and either rationalize or trivialize the problem, depending on the situation.
Try tapping exercises.
Tapping is often referred to as an Emotional Freedom Technique. The theory behind tapping's usefulness is that "negative emotions are caused by a disruption in the body's energy system and tapping can restore balance to this system. It purportedly neutralizes any judgment you have about your anxiety and removes limiting beliefs you developed in the past that contribute to your anxiety" (Alban). There are quick, short videos teaching you these tapping exercises all over the Internet, and once you've invested those few minutes into learning the motions, you will be able to employ them anywhere you are.
Try the 3:3:3 rule
In order to employ the 3:3:3 rule, you must name 3 things you see, name 3 things you hear, and then move 3 parts of your body. This grounds you back to reality when your mind is reeling, and you are able to focus more on yourself and your surroundings than you were able to before.
Buy a book with easy mind puzzles.
These are perfect to get your mind off one thing and on another. They keep your mind occupied and focused on figuring out the puzzle, clearing room in your messy mind. They can be crosswords, sudoku, word searches, or more: whatever your heart desires!
Meditating.
Meditating is proven to calm down your mind, slowing down those anxiety-inducing thoughts. It also enhances your self awareness, and it helps you feel more grounded and clear-minded to make decisions or to focus.
​Read, read, read.
Reading allows you to get lost in a world that isn't your own, and sometimes, we all need that break from reality. Your mind pushes those anxiety-inducing thoughts aside to make room for a more centralized, straightforward plot line, and an enticing story makes for the perfect distraction.
Go on a walk.
Finally, back to the basics. Going on a walk raises endorphin levels, and you are able to enter a meditative state that clears your mind and alleviates the anxiety. And fresh air always helps.