To achieve emotional balance I believe that to achieve it we need to have a good physical or mental control is like having a lot of self-confidence and a positive spirit full of optimism

I'd say balance is everything in life and without it, you have nothing. You're in a tough position as caring for a cancer patient it not easy. I've done that and unfortunately I'm speaking from experience. I wish you all the best and may God give you the strength you need. Also I wish all the best to your sister.