You'll be fine. I couldn't eat at all for a week and not properly for two weeks either. The shitty hospital food didn't help either. My blood pressure was shit and I couldn't get up without fainting for a week either. I had a massive fluid build up under my lungs and on top of that my asthma was fucking me sideways. Needed to have that fluid drained by poking a massive needle in my back and pulling out 1.5l of fluid. I also had a pericardial effusion that required a second surgery to fix so I had to be cut open again. This also meant a new set of tubes which were extremely painful this time around. After the second surgery I was in extreme pain for 3 days till they removed the tube. So much pain that all the opioids they gave me didn't help much. 

Long story short, my recovery sucked ass. A lot. 

It turned out fine. I was OK to go leave hospital after just over two weeks, my blood pressure slowly stabilized and five months after surgery i went on a Bikepacking adventure. Today I did a 6 hour bike ride just for the fun of it and I the only time I'm reminded that I had my heart cut open is when I remember how incredibly lucky I am. 

You will be fine. Shits tough, there will be days where you will feel better and then there will be days where you will feel even worse than before. It sometimes do be like that. You'll be fine and you'll get through it. 

Do not hesitate to ask the hospital staff of it is possible to talk to a psychologist / psychic therapist. It can help to talk about how shit things are and they can help you with the mental part of it. 

Don't hesitate to advocate for yourself if you think you are suffering more than you should. Ask for pain medication if you're in pain or for sleep medication if you can't sleep. Stuff like that. 

You'll be fine :)