My grandma lived with us almost my whole growing up life. In the last 7 years of her life, she became increasingly frail and needed more and more attention/help. Her mind also started slipping, and she became increasingly difficult to get along with. It was hard- plain and simple. Here are some things I personally learned through the experience that I would implement in my own household should this happen to me someday:
1. Maintain or create family traditions that only involve your own, immediate family. Maybe just you as a family going to a high school sporting event and then out for pizza each Friday night or something. Of course you have to be careful that you don't hurt your relative's feelings by leaving them out, so you have to carefully think through what you can do.
2. Listen to your kids' frustrations with the situation or their sadness at the loss of what family life used to look like. Major changes are hard, and your kids should know that they can talk to you privately if they need to express emotion about what's going on. Stay on top of their feelings, particularly if the person living with you sucks a lot of energy and time out of your day.
3. Get headphones for the TV if your relative is hard of hearing and watches it a lot. My grandma refused to wear hearing aids, and for about a year the TV blasted all day until we thought we'd lose our minds. When we got her headphones, she could watch it as loudly as she wanted, and the rest of us could live in peace.
4. Don't try to make them eat if they don't want to. I remember years watching my mother painstakingly try to make dish after dish that my grandma might eat. She was stubborn and not hungry, so she constantly refused. My mom was distraught. You cannot make an adult eat if they don't want to. So serve normal food and let them choose. Don't take on guilt if they won't eat. Try to supplement with Ensure or something if you can.
5. Call for help. If you're in care-giving mode, you simply cannot do it alone. Get help and know that it's not being a bad son or daughter to admit that you can't do it all for your parent. If someone offers to help, never say no.