Caregiver fatigue is a very common situation. I watched my father & sister (who managed the majority of my mom's care before she died) & they were stressed & exhausted.
I watched how very numb they were & the slow return to life they are experiencing.
Parenting our difficult children, in my humble opinion, is a different fatigue. It's lifelong - there is very little closure with a mental/emotional illness.
That is where respite & self caring comes into play. Even the best of us crack under the level of pressure our little wonders bring into our homes.
Take care of yourself.