So we're talking damage limitation now. And I think the main thing to do is to accept that these things will happen from time to time and then remember to redeem it when you've come back to center once again. Go lock yourself in a bathroom for five minutes, splash water on your face and remember to breath. Do NOT worry if your children are crying or banging on the door - that's fine, they're upset, but being upset never killed anyone. You are their world and you are working on coming back to yourself.
Once you rejoin them, say something like "Wow! Mommy was really angry! REALLY very cross. Wheewf. It's gone now. The Big Angry Mama Bear is gone now. " And playfully attack them with pillows and laugh or give them a cuddle - depends on how your children react to such things. Some need boisterousness to get past trauma, others need peace and quiet.
Children NEED to witness anger and fear in adults. But it is the second part which makes the difference between frightening and possibly harmful situations and those which are about learning to be a full human being. And this is the transformation. It is our job as adults to transform the sadness or anger and let our children witness how we get back to center. Esoterically, to be a witness is as powerful as actually doing, as acting. And for children it is inestimable.
Just think how children who are in childcare for most of their days - or Waldorf kindergartens - do not get to witness and live through all the human experiences which make us full human beings! That was one of the truly awful things that struck me in the aftermath of Hurricane Katrina - this desire to pack the children off immediately to school. How strengthening it would have been for those children to get to live through an experience of adults working to overcome their grief and their tragedy and build something new instead of shutting the children off in their sterile schools where, I guess, they could read about human tragedies in social studies textbooks....
This is one reason why it is universally recognized that homeschooled children - of whatever method - are more mature and can fit better in all kinds of social situations than those raised en mass in schools for most of their lives. So embrace the pain! It is a gift of being at home with one's children.
Back to the subject at hand...I have had, actually, the experience many times that when my sons are being particularly awful, that a real blow-up diffuses the situation. My eldest in particular, who is a very intense person, continues at 17 to be much calmer and centered after we have had a big argument. He becomes more and more "in your face" and demanding and somehow needs the release of an argument to work through whatever it is that is mounting inside. Of course at his age (once all is back to normal) we discuss what it was that led up to the explosion and our (his Dad and I) observations on how he appears to need such a release. We work to help him understand what is going on inside him so that, as he matures, he no longer needs to explode. And over the years, I can honestly say that sometimes I choose to allow myself to yell at him - I have learned, over the years, how to work on my own strengths and weaknesses so that I am not merely reactive when my sons pushes one of my triggers. He somehow needs me to yell - my hope is that as he grows up he will no longer need this as he becomes more self aware.
Could you be expecting too much from your children? Might your picture of what you "should" be doing be too high? I am a little wary of your phrase referring to your children's "power" - I know it can feel that way and twins can run anyone ragged - but tiny children do not have "power". They can certainly push our buttons and some are extremely adept at that - but there is no power involved. To wield or use power necessitates consciousness and focused will. Less-than-four-year-old children have neither the consciousness or the will forces to exert power. Anyway, after you perfect the art of regaining a lost center, don't blow it by then beating yourself up with guilt!!!