Be organised, spend time first thing and at intervals making sure you are organising, prioritising effectively, delegating where appropriate (especially if you find it hard to let go of things/control to others) and slot in de-stress breaks regularly, even if just going to make a coffee.
Don't just focus on the work, focus on the changes you can make to help you.
Kalms tablets can be good and rescue remedy and things like camomile tea for major stress moments. If you tend to hype things up and let them overwhelm you, especially if you tend to over exaggerate, you could have little postits with trigger words on like relax, breathe, rationalise etc... They can even be less visible like a bracelet/charm/stressball/photo, something to focus on to calm you, even something that just makes you smile/laugh.
Could work help you phase back in and try to help you with your stress levels?
Long term though, unless you can handle the stress, get out of the situation, it's not worth it if you can find a different job where you are less stressed.