Pulmonary Embolism Support Group
By far the most common form of pulmonary embolism is a thromboembolism, which occurs when a blood clot, generally a venous thrombus, becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs. Symptoms may include difficulty breathing, pain during breathing, and more rarely circulatory instability and death.

I hate to say this, because if it were easy, we'd do it, but we have to allow ourselves to relax and let our guard down a bit. Hard to do after a crazy event like a PE.
Thanks for the advice, I appreciate it.
Thanks for the advice.
Yeah, right after my PEs I was so incredibly aware of my breathing and heart rate that I wasn't even really sleeping because I was so stressed about it. That has slowly faded (I'm five months out now) but it still pops up at times.
That "super-vigilance" is hard to control because, for a lot of us, being aware and persistant was what saved our lives in the first place and we're really concerned about turning that off now.
Honestly, I think the anxiety is part of the healing process. Your body and mind are dealing with all the stress the best way they know how and sometimes being really alert is what we feel like we need to do. As you discover other coping mechanisms and start to become more familiar with the "new normal" I think it'll all start to become more manageable.
In the meantime, hang in there! It does get better!
Take care!