I've had lots of surgery, much of it life saving as well as for quality of life such as my double knee replacement. As others have said, rehab is critically important for a good recovery. And while rehab can be painful, at least you know that it is getting you better, not doing more damage, so psychologically it is easier to work through the pain.
As to your shoulder surgery, I hope for your sake that you have gotten at least a second opinion. I don't care how good your surgeon is, getting the input from another qualified surgeon can mean all the difference in the world. For one thing, the second surgeon may not recommend surgery but only physical therapy. Shoulder surgery is notoriously uncertain in its outcome, and surgery should be the last, not the first option. I'm not accusing, but sometimes the motivation to recommend surgery might involve more than just what is best for the patient. The first surgeon might have a light schedule, plus wants a new big boat. Seriously, get a second opinion, preferably from a staff orthopedic surgeon at a teaching hospital. If both surgeons that examine you agree on the necessity of the surgery, even then they might have different ideas on technique. I had to have a kidney removed due to renal cancer. The first surgeon's technique, what he was trained in decades ago, involved removing a rib and adding a year or more of painful recuperation. The surgeon I eventually used was a teaching staff surgeon at a university hospital, who uses a more modern technique that allowed my ribs to be untouched. Still a few months of painful recovery, but not a year or more as it would have been had I gone with my local surgeon.
FWIW, I have torn rotator cuffs in both shoulders. Lifting anything more than a few pounds higher than my shoulder is difficult or impossible at times. But I have had extensive physical therapy and for the most part can live a normal, active life (I have no trouble handling my Honda Goldwing, over 900 pounds, despite the bad shoulders at my age of 76). Rotator cuff surgery, in my opinion, should be only done if absolutely necessary. Good luck.