i have had these feeling as well but they stem from a bad tuna incident where if u eat bad tuna it will speed your heart up and it really freeked me out , because i was out on bussiness out of town by my self and i woke up thinking i was going to die alone in a hotel rrom. it took about 5 months to get over , but recently got triggered when i was driving home one night and passed out at the wheel..after my wife and mother got into a huge fight...inbetween all this my daughter was born..wow when it rains it pours dosent it..the thing i have found helpful is rollerbladeing and while i do that i go through all the goo things in my life and just think about that, also tell my self that its all mental and i am physically healthy, as i have gone to the doctor and had all kinds of tests on my heart and have the all clear...hope this helps.....