Please read this - whatever stage of supporting a loved one with dementia. It will help you to focus your energy (not waste it) and minimize the overwhelm / anxiety.
Print it out.
Commit to doing some thing(s) every day, no matter how little.
You want to avoid burnout and this is one major tool is doing this.
Stay as healthy as you can. While Teepa may not have mentioned getting enough sleep, exercise, meditation, getting outside in nature, eat a health-focused diet . . . this is critically important too.
In my case, and probably some others, I actually turned down an offer of support by a friend. My thought was, “yea, sure, what do you know about dementia care?”. That was sort of foolish because not only would it have provided me some respite, but I didn't know anything about dementia care myself!
I especially like her suggestions about building a "team". Too many folks try the "lone ranger" approach which always leads to burnout.