Racing nerves can throw off your focus when it matters most, but simple...

https://astro-wiki.win/index.php/Process_Focus_vs_Outcome_Focus:_Why_Outcome_Thinking_Ruins_It

Racing nerves can throw off your focus when it matters most, but simple breathing helps calm the mind. Try a 4-count breath in, then 6 to 8 counts out to steady yourself before a lap