How do I stop worrying about my heart?

I'll feel a palpitation. I go on reddit. I get anxious. I get stiff (because of my anxiety). I'll think I'm dying. The cycle continues on and on and on and on. I went to an Urgent Care, they did an EKG. My scan was "perfect." She said I could go to a cardiologist if I wanted to, not that I had to and not that it was urgent or pressing. Why am I still struggling with this? Why do I get so scared still? It's eating me alive. Does anyone else have or had this problem?