Might try this

https://health.clevelandclinic.org/box-breathing-benefits/

Can you identify what is causing it, specifically? Then analyze the cause and develop a plan and consider if it is really worth stressing about. Usually the source of the anxiety is something that is not very important. Usually, it is your brain f'ing with you - seriously, Your brain is sending you false signals/emotions and you have to ID those and tell them to go pound sand. Are you going into battle? Having brain surgery? Taken hostage at gun point? Those are valid anxiety reasons. If you have someone you trust, ask them if your reason for being anxious is valid and why it is not something to worry about. A third party perspective helps. You might want to research GAD (generalize anxiety disorder) to learn coping tips.