I read the article and I can see how this can happen if you're not mindful of your own needs. A good friend gave some great advice to me some years back and warned me not to give up my job to babysit as she had done that with awful consequences. She felt isolated, lonely and taken forgranted, so she went back to work and used the money to pay for childcare. She said she didn't care she was working for nothing as having some adult contact meant much more to her. This also meant that any resentment she had towards her daughter disappeared and the relationship was better as a result.
I currently work full time, but I do try and help out with looking after my 4 GC. However, I already talked to my children and explained that when I fully retire, I am not going to babysit full time, if at all. I told them that I want to travel and although I love them dearly, having worked all my life and also been a carer for many members of the family, I feel I deserve a break.
I think the important thing here is to think of your own needs and fit helping out around that. I don't believe that being a martyr serves anyone. With the best will in the world, we don't have a magic wand, it's ultimately their responsibility, as our children were to us. Support by all means, but not at the detriment of your own health and interests.