I had a mastectomy and lost quite a few lymph nodes and my arm certainly wasn't useless. My underarm didn't belong to me for a while, it's true, but I had full mobility within days and I went back to work after a week. Everyone's experience is different, so it's good to be prepared for some setbacks, but it also means that sometimes things go pretty smoothly. "It is what it is" is a very good thing to keep in mind, also it's good to avoid expending a lot of nervous energy on things that may not happen. It's hard not to plan and anticipate, but it's more effective to wait till you know what you are facing, and deal with it then. Best wishes.