I was in pretty good shape before my surgery but it took me many months of recovery before I felt like I was 'back'. I also had severe pericarditis post surgery that slowed me down for the first few months... they gave me colchicine for that problem and it seemed to help. There were many times in the first few months post surgery that I felt tired, out of breath and weak but I kept pushing which is what I'd recommend for you as well. I am now almost 2 years post surgery and am back to hiking in the Rockies, walking and biking so things will get better over time. Good luck and hang in there!