Feeling jittery before a race is normal, but staying sharp is key. One handy...

https://kylersbestjournals.capitaljays.com/posts/regulation-167-of-the-human-medicines-regulations-2012-explained-simply

Feeling jittery before a race is normal, but staying sharp is key. One handy trick is to breathe in for four counts, then out slowly for six to eight—this helps calm the nerves