Not that you would wish your life on anyone I know, but have you asked that question?
I was often told that God only gives us what He thinks we're strong enough to handle. Guess that means you're strong enough too.
It takes a strength unlike any other to keep smiling each day despite the pain in your body. You are strong enough for this life! and you are strong enough to live it!
Do the best you can each day with what you have...take good care of you ok?