When is it Enough?

As a general question...when is it enough? The word "enough" could mean anything, but for me "enough" means my limits. How and when can I say "enough" because I am at my breaking point. I have to admit though that this summer with Danielle home has been wonderful. No worries about hospital visits (even though we did have one and it was minor), but everything was workable. But there are those times where I just want to scream at the top of my lungs and swear, throw and real big adult tantrum because of the lack of respect that is shown to me as "mom". I can start out real calm in trying to teach Danielle some pointers to a cleaner kitchen but then she starts raising her voice, slamming kitchen cabinets and stomping around. My head starts pounding, I feel my blood pressure rising...then it's like Mt. Saint Helen's erupting. I just know that I need to send her to her room, which she refuses for a while, then she calms down, then goes to her room. There are so many times I want to throw in the towel and run away but when Dani calls me to read me a poem she wrote or a story, or how improved her reading is, then I move right back into my heart and soul. Like I said...it's an adult tantrum so somebody should put me in time out!