I agree with what other people have said, Better to end up with a short time enjoying being with the grandchildren than a long time which takes its toll of you and your relationships and your health in the long term. So time to look and see what interests and courses are available to you now. Learn something you have always fancied doing but never had the time before, so you might learn bridge or backgammon or go dancing or painting or whatever. Book the course and start on it and then you can say pleasantly, oh sorry you are not available on tuesdays and fridays etc. Then progress to having a day out with these new friends or your partner just to go for a walk or drive down that road you never tried before. So you are still around to do things with your grandchildren, but in a manner that is more fair and will not end up in resentment. Of course your children may resent the loss of their free childminder on tap, but eventually you may get to a point where they appreciate you and your grandchildren are happy to be with you and may learn some of your new skills too. Carrying on as you are doing, seems to me to be a recipe for , resentment, ill health and possibly ending up where you do not feel able to be involved with the grandchildren at all which would be a shame. You want to have a relationship with them where they are pleased and happy to see you and share in things you enjoy, not to be seen as the ever available dogsbody who will give up her own life and pleasure and health for these rather selfish children. Practise this next month and then your new years resolution of not being available at the drop of a hat will be easier to fulfill. Good luck and let ups know how it goes!