It is so hard to explain. It is a balancing act. People who do not live with a chronic condition really don't understand, regardless if you "try" to explain it to them or not. Even those that see you on a daily basis have a hard time understanding. And, MS is tricky. We can feel good one day, or minute, and awful the next. That makes it more difficult to explain.
Most of the time, I don't bother to explain. I just say, "I'm having a bad day" and leave it at that. It's much easier. Most of those that I am close to understand that and know what it means.
Hang in there B2Y

and when you find the balance in "explaining" let us know.