This is something I've been practicing for a few weeks now, read it in a book.
The brain takes in sensory information (emotions, body language, images, etc.) that cause anxiety. For example, someone could laugh behind you, and the laughter is processed by your brain and it tells you that the person must be laughing at you. Another example could be during a conversation someone makes a remark that sounds negative, and your brain assumes that the person is mad at you or judging you. These thought patterns almost become automatic and the more we accept them the worse they become.
Practice noticing EXACTLY when these anxiety causing situations start to kick in. It's hard at first but gets easier with time. Then sort of hit the pause button and ask yourself why the person would have any reason to laugh at you, or why someone would be judging you. Most of our thoughts are irrational. Learning to notice these thoughts when they occur is the key. Use your mind to translate these deceptive brain messages into reasonable thoughts. Replacing these negative messages with what they really are is super helpful.
I've been doing this for a while and am really starting to get good at it. As soon as I feel an anxiety arousing situation I've been sort of replacing the negative messages with positive, realistic ones and can calm down my level of anxiety big time.
For example, In Psych class yesterday we had to give a presentation, and of course my brain makes me feel like everyone is going to notice everything I do wrong, think my speech is slurred, or judge my every little action, so before the presentation I was feeling really anxious, so I kinda just took some deep breaths and told myself that my thoughts were irrational and that honestly, no one else really cares what I do as long as I give this presentation. No one has a reason to judge me. Overall the presentation went really well.
Essentially the brain reacts to the environment in automatic ways, which often result in anxiety. With your minds, we have the ability to realize that the reactions our brain makes are irrational, and we can replace them with positive and more reasonable thoughts. Don't let yourself become wired to your brains automatic and deceptive thoughts. Instead, use your mind to react to situations and make decisions!
Give it a shot! Hope it can help.