I've had breathing issues in the past due to a deviated septum that has caused some issues with my lungs and my nose. It also assisted with causing my heart murmurs with my past jobs.
Surgery done to the nose aside, everything restored to a natural enough balance enough that it's mostly natural feeling, and one cannot tell anything else was done to fix the problem (surgery and re-adjustment to new conditions).
Nowadays, I'm surprised with the kind of hostile environments I can live in, and be minimally affected by. But also thanks to living next to the ocean, I've also been able to speed up the healing/adjustment process. The supplements made the process damn-near effortless.
What I can also advise that may help is to take at least a yoga class or 2. I was reluctant at first, but after a few sessions (and it's been some time since last session I attended), I've managed to patch up a few more problems throughout my system, from back alignment, to organ operations. I ought to go to another session sometime now that hibernation season is over. I need to re-adjust so I can jump into the ocean before it warms up completely again.
All I can really say that can also help is don't worry about it too much. It'll just be more excess stress you don't need. Follow your natural instincts on how to fix yourself up. It's at least 75% correct on what you need to do to be on your feet. Works for me at least.
Oddly enough, I would normally go against the doctor's advice, and be active. You can't make the heart stronger without activity.
Recent Sad: I just accidentally broke a pretty awesome sand dollar I had when adjusting my speakers.