Hang in there and hope for the best but accept where you are now and work on getting better. My case was much worse due to polymyositis and I have lost permanently an estimated 35-40% of my muscle cells so there are things I can't do or shouldn't do to avoid injury. I can ski well, play golf ok, but even jogging is very difficult so I stopped even trying. Just as well since I have an accumulation of knee/hip/back injuries over the decades from variouos sports/activities and with weaker muscles you risk further joint injury.
My attitude is to be grateful that I am alive, standing and can do what I can. At my age I shouldn't be upset about loss anyway but I am glad I can still rip on skis. Endurance activities like hiking and climbing can be done but on a much less challenging basis and running is out. 40 years or more of running is enough. I work out frequently and am trying to improve both my fitness and strength before the ski season so I have not given up.
Good luck and be patient. Lupus can be tough disease and men tend to get it later in life with very severe symptoms. Treatment is over a period of years and since it cannot be cured it is always there to screw up your life. Meds alone can mess up your body. My lupus was in remission for 8+ years and out of the blue attacked my liver and blood. Liver ok now but still wrestling with low platelet counts. 2 months of steroids improved things but who knows if my platelets will stabilize at an acceptable level or not without treating lupus on a longer term basis. Did uber doses of steroids in 2015 which raised my platelet count but was down to almost 0 again this spring. Next step for treatment probably IVIG if they go down again. After 11 years this almost seems normal and I don't get upset about it....more of a nuisance. Just glad to be alive.
BTW, while my skiing is as skillful as it was 20 years ago my age and strength dictate no racing (I was a racer and coach), no bumps, no trees, or ultra steeps. Just the same what I can do under good conditions is great and most people at this stage of life have given up sports like skiing. Impatiently waiting for cold weather again.
MCTD (SLE Lupus, polymyositis, scleroderma). Diagnosed 2005. Kidney, liver, GI tract, dysphagia, raynauds, barretts esophagus, quadriplegic in 2005. Recovered and now active in downhill skiing, golf, hiking. Meds: amlodipine, benezapril, omeprazole, potassium, folic acid, vitamins, maxide.
Remain Optimistic and you can overcome.