hang in there. It's hard sometimes, but these are the moments (the good and the bad) that you hold onto forever. You'll probably feel and see things that alot of people never will. you'll see a strength in your mother that you never have before.
That is a gift and your honour...
Keep up the great work...
The important thing I think, from experience, is to try to carve out time for yourself at least once a week.
It can be hard, because you feel like you will miss something, or maybe feel a little guilty, but it will be good for you and for her (she'll have the best of you that way) if you can try to get someone to cover you while you duck out to the gym for an hour, take a walk or chillax to some good music....