Try the “4-7-8” method which focuses on your breathing to slow your heart rate. Dr Weil, American MD says “Practising regular, mindful breathing can be calming & energising & can even help with stress-related health problems ranging from panic attacks to digestive disorders”.
Exhale completely through your mouth, making a whoosh sound.
Close your mouth & inhale through your nose to a mental count of 4.
Hold your breath for count of 7.
Exhale completely through your mouth, making a whoosh sound to a count of 8.
This is one breath. Now inhale again & repeat the cycle 3 more times for a total of 4 breaths.