I second the idea of relaxation techniques. A really simple one is square beathing (look it up in mindfulness books ). Take a deep breath in while counting to 4 in your head. Hold it for 4. exhale slowly for 4 . hold again for 4. repeat as needed . Physically, you are squeezing your heart with your expanded lungs, which will help to slow it down. Mentally, focusing on counting may help to distract you.