I'm an old gym rat, but I'd agree with pellicle on this one. When I had my valve replaced, my mind was chomping at the bit to get back to exercise. . . but my body wasn't all that interested. In fact, I had so many complications after surgery, I was not cleared to enter cardiac rehab until 12 weeks post-op. After that time, I had to take it gradually, to say the least.
Fast forward about 6 1/2 years, and other than the bump on my upper chest for the pacemaker, you would never know I had open-heart surgery. I'm no kid, either, as I am nearing 70 years old now.
I relate this to you so that you can realize that pellicle is right. You may feel the emotional pull back into exercise now, but it is probably best to resist that tug. Let your body hear properly and fully, and it will reward you with a lifetime of good service. I am doing as much now, and more, than I did pre-op. It took a while before I felt up to pushing hard, but when it felt right, I did it. I "got it all back" and then some. Just let nature take its course for a while. You will get back to where you were, and then some.