Don't make any rash judgements about your future life based on how you feel right now. Many have felt much the same as you have and as things improve gradually, they start to realize that they are not going to fall apart.
For Heaven's sake, if anyone was going to fall apart it would have been my husband. He's had 3 valve surgeries, 2 lung surgeries, has a pacemaker, has CHF, has pulmonary hypertension, diminished lung capacity, had a massive bleedout after gallbladder surgery that almost put him six feet under, had the most terrible case of serum sickness that anyone had seen in 17 years. He almost died from that as well, I was told not to go home.
Last year at about this time, he was in such terrible shape from severe pulmonary hypertension and kidney failure and Stage 4 CHF, and severe anemia, that he was slipping into a coma. He spent a couple of weeks in the Heart transplant Unit of the teaching hospital here, and another couple of weeks in the critical cardiac unit.
He's still here and improving every day. He can walk over a mile on the treadmill and do light weights as well. He's 72.
And Joe's not the only one on this board who's been through many meat grinders. All kinds of stuff! We even have a member with 5 valves, one manufactured one outside her heart. I hope she tells her story, it's very interesting.
So---your body is much stronger than you could ever imagine. Don't give up hope. You REALLY, REALLY will get better, I promise!
Don't think of taking big steps right now, just take little baby steps and they will build on each other.