Agree with @lindy9
Was told to avoid caffine. It will speed up your heart rate and body. You want your pulse to remain steady as much as possible and not be affected by other stimuli.

There are a lot of foods and drinks with high levels of caffine. Many of these energy drinks and electrolyte drinks are full of it.

I and many other also found that doing a hobby or exercise that you like doing will help reduce your stress and anxiety. When you reduce those it has a calming affect on your heart and body. It can really helped. Just find something you like to do and do it.