On this side is your responsibility. On the other side is their responsibility. Make it very clear in your own mind which is which.
Take full responsibility for your side and stop right at the boundary. Whenever you are tempted to cross it, tell yourself to stop.
Remind them of their responsibilities but do not do it for them.
(Whenever you cross the line, you are shouldering their responsibility for them. They fight against you is because they know that's the way to get you to do their work.
Love yourself more. You don't have to take care of everything in order to be loved, like you probablely did when growing up.
Check your emotions. Treat it like a business.
It is very hard to place the line. The tendency is not to have one, so that if anything goes wrong you can say to yourself: I did everything, I'm not the one to blame. It takes courage to have that line. You might feel easier without it, but you pay a price with your physical health and mental sanity (you might feel happier without the line, but since you're not happy, it indicates that you have a line but keep crossing it.)
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