Glad that you are doing better, don't push the return to your pre-attack level of fitness hard, anxiety about that, coupled with the worry in the back of your mind about another MI can weigh heavy on your heart (and not in the metaphorical, mushy stuff way.) I had to find a means of shedding the anxiety from a heap of major surgeries between 2000 and 2010, developing chronic kidney disease and now Parkinson's Disease. Stress kills, big time, anxiety is stress being manufactured, I hope you can find a means of releasing yourself from the stress so you can continue to recover well and get complete rehabilitation of your cardiac system.
Many of our members, as shown by the number of replies so far here, have experience with heart attacks and the recovery from them. I am very fortunate given my family history of heart disease death that I haven't had anything, my one cathertization was very good, the cardiologist said I had sewer mains for coronary arteries (as a civil engineer I wasn't quite sure how to take that one

) Getting torn away from your old levels of activity has gotten you down mentally, and that is wearing on you as much as over training can be. There have been recent threads here about cyclist getting sicker, having cramps in their legs and other maladies from their exercise level being cut or stopped, you seem to be in that category. I can personally attest to that one, when I get slowed or stopped I can feel the PD getting worse for a bit.
Use your friends, and you have a bunch of new friends here, now, and your family to buck yourself up and let things just go when you feel the worries getting out of hand. I hope you will keep us posted on how you are doing and your progress, best of luck with everything, you are added to my prayer board list.
Bill