I DO know what it's like.
I've had ten carees in total. My son was brain damaged at birth in 1979, he can't read, write, or do any maths. In addition I supported my mum for over 30 years, by the time she died she had 28 different things wrong with her. The last year was spent in a nursing home, the hospital said that even if she had live in care, she was too ill to live at home.
My husband DIED when he was 58, I found him dead in bed, having had a massive heart attack. This is the reality of trying to do too much for too long. His mum had dementia and his dad had heart failure. At one time our son and all four parents were all entitled to highest DLA care!
The day after I was discharged from hospital with a massive scar right across my stomach, Mum summoned me to her house 6 miles away as the carers had mucked up her door lock and I was the only one with a spare key! The doctors even tried to bully me into caring for mum, who had taken to her bed. It turned out that she had broken her leg a week earlier.
On the verge of a nervous breakdown, newly widowed, newly disable, in constant pain, I was given some counselling sessions, which changed my life. I was encouraged to set priorities, son came before mum, he couldn't speak up for himself, mum could. I should feel proud of what I did, not constantly guilty about what I didn't. Most important of all, was being given "permission" to put my health needs first.
What good are you to anyone if you are ill? If you don't put your own health first, no one else will. MIL is totally self centred, she NEEDS more help than you can safely give. My mum's nursing home was lovely, I could come and go whenever I wanted. Residential doesn't mean abandoning someone. MS is a progressive disease, at some stage there will be no alternative to nursing care.
Don't be a martyr, put your own needs first. It's a bit like the safety announcement on a flight. Put your own oxygen mask on before helping anyone else.