I haven't read any answers, so I may be repeating. I applaud you for recognizing first that you are human and can make mistakes. We are ALL humans, emotional animals and knee jerk reaction specialists. Nobody is immune from these behaviors.
I know you are going to get better simply because you know this is a negative and stressful situation for you and your family. I remember a very wise adult describing this as a "kick the dog" scenario. Whenever someone is super stressed, they take it out on the people they love the most and they know won't shut them out.
I guess my words of wisdom are to let tell you know that you are loved. Maybe a ADHD child wasn't in your life plan and that is a very difficult card to be dealt in the great poker game of life. But, you can do this!
Just like you would give your child small rewards for behaving in a positive manner, you can do this for yourself! A mani/pedi, cute blouse or splurge dessert. Reward yourself for rising above in a heated and difficult episode. You deserve the treat and the break!