Sometimes it is just beyond you. No one should underestimate how difficult it is to care for one elderly or infirm person. Your parents physically couldn't do it anymore and even if you're younger, you're only one injury away from not being able to do it anymore yourself.

Sometimes the other people in your life also have demands on your time that make it hard for you to put your entire life on hold and become a full-time+ caregiver.

It is a really tough situation, no matter how it ends.