True enough. My mum had her moments but generally presented as compos mentis. A downside was that she would keep saying "Jennifer, this may sound paranoid but...", forcing me to provide a reality check. She would work until she got too ill, go into hospital, get back on the medication she'd stopped taking thinking she was fine, recover and the cycle would continue.
I didn't realise just how tiring it all was for me until it was over.