Children do need discipline but the discipline has to be based in compassion. That's how we stop getting angry at them. One of the things that helps a great deal is not to look down on children, they are just little people. Sometimes we don't actually believe in their capabilities, often as much as we don't believe in our own. But if we treat them as little people, often times this potential will be drawn out.
I knew a meditating couple who had a 3 year old and a 6 year old, and taught them many things. One little story that may help is about the 6 year old - one day there were only 3 pieces of fruit for the meal and so the mother decided that everyone else should have fruit and she will go without. The little 6 year old looked at the fruit and said, "No, no, that's not fair!" And the mother said, "it's ok, you'll get your bit." - "No, no", he said and ran away. He came back with some paper and started to draw three circles. Then started putting lines through the circles and by this time the mother, the father and the other kid were looking and wondering what the little boy was doing.
After a short time, the little boy's eyes lit up, "Here, if you cut the fruit this way, then everyone gets a piece the same amount and nobody has to go without. By teaching the little 6 year old about sharing and generosity in a way that he could understand, this child developed in beneficial qualities - it drew out what was good in the child.
Yes, we need to give them discipline, we need to teach them what is right and what is wrong, but we need to do it in a compassionate way, trying to encourage the strength and not just focusing on the weakness. And to have patience and understanding that a child will act in ways that are difficult for us at times. This will help prevent us getting angry.