As long as you know -- for yourself -- what your limits are, and what your boundaries are, and how you plan to enforce those boundaries (be specific) then there is no harm in trying one last time. Just be careful: for many of us, those "one last times" stretched on for years, because we had not yet thought-through what had to happen before we'd say, "Okay. I have to be done now."
Protect yourself by thinking it through. Ask the questions. Know what you'll do if it doesn't work, and you will be just fine. I'm that kind too - it's good to know I've done all I could. As long as the "all we could" isn't a moving target!
