How do you keep your spirits up when you are caring for your mother who has dementia?

I love my mother very much and care for her daily. I do have caregivers that come in the afternoon so that I can go home and try to relax. She also has graveyard caregivers. But when someone doesn't make it to their shift I end up working it, no matter the shift. She can become delusional, verbally abusive, and verbally aggressive towards me and can single out a caregiver to the point that I have to replace that caregiver. I am at her home everyday and am exhausted. I get calls from my mother when I am home trying to relax about her delusions about a caregiver. It just never ends. I have 2 brothers but they don't help out.