Can't add much as others have said it for me
Make a list of what you do for your sister and what is really necessary to help her
Make a list of what you do for her children and what is really necessary for them
Make a list of what you will miss when you begin to say 'no' - it really does become easier with practice!
Put yourself first. Tell them that you will be unavailable during the year due to your own health requirements - you do not have to go into detail or justify yourself. If they ask why tell them what you want to, personally when I was going through breast cancer treatment the LAST people I wanted or needed were family members
Ask DH to help compile the above - you will need his support during the pre/post op periods and he needs to be able to tell you what he will be able to deal with.
Resentment eats away. This day I am posting a letter to my sister telling her that we are no longer buying presents - see my birthday thread, she gave me a bar of soap for my 60th
- Mum steps in to tell me that my sister is having trouble at work, is having to bail her sons out financially - sod off, those are her choices, my birthday doesn't suddenly appear on the calendar
- it's because Mother has always bailed her out that she is as she is - narcassistic and not organised!
Punch a cushion. Works for me