Being there when needed. Helping loved ones.

This recent scare with my Mom has me questioning how others with mental illness handle stressful situations.  Are others always reliable?  Do they do fine during the crisis, then tire out?  Can they even handle the problem?  Being the only person my mother has to help her, I need to be there for her physically and mentally.  But I am embarrassed to say I have had to cancel some of her appointments because of exhaustion from depression or terrible panic attacks.  She understands completely.  But that does not take away the guilt I feel.  The situation is not so severe that a visiting nurse needs to be hired.  But there are days after emergencies I am so wiped out, I do sleep the next day or so away.  I also wonder does anyone who want to help their loved one, but they feel unreliable?  My mom has been there for me in so many ways, I want to do the same for her.  Anyone reading this post who can relate, please comment.  I could use any advice or just any experiences.