A little but ago, I was having a bout of anxiety (as one does) and my chest was hurting more than normal even though my resting heart rate wasn't abnormal for when this happens (about 90bpm). For some odd reason, the idea to hum and hit my chest with my hand crossed my mind and you know what? It worked! My bpm afterward was down to 72!

I'm not a medical professional at all, but I thought I'd make this post so y'all can try and maybe it'll help.