Consistancy

Why is it so hard as mothers to be consistant with our children? When mine were young it was a constant battle to follow through when I was attempting to discipline or instruct my children.
To often we say,"if you don't do "such and such" I am going to ____. Then when the particular action happens we forget to follow through.When that occurs over and over, the children very soon learn that mom does not really mean what she says. then the mery-go-round starts. Children misbehave, we threaten, children misbehave again, we threaten again, and so on and so on...... Our frustration rises... we don't understand why our children don't listen.... we get mad.... children get frustrated....
What is wrong here? It is the lack of consistancy. When we tell our children to so something or not do something we should expect immediate obedience. If that is not forecoming then proper discipline should be promptly applied. It will not take too long before the child realizes that we mean business. If we tell our children that they are going to be punished if they do something, then that punishment should happen the first time, not the third, fourth or fifth time.
Life will be so much more orderly, pleasant and much less stressfulfor you and for your children. Many parents do not realize that their children like order, continuity, and structure as much a we do. It gives them a great sense of security.
Any thoughts?