A: Dear i_m_huges:
Your son has begun to tell you "NO!" because he has discovered that he is a separate person from you, with his own feelings and wishes which are sometimes in conflict with your feelings and wishes. Congratulations! He has taken a big step along the long road of becoming an independent, self-reliant individual. When he says, "NO!" he is asserting his own healthy individuality. You do not need to make him stop saying "NO!" to everything--after all, it doesn't really matter what he says; the point is that he is feeling disrupted and annoyed and your goal is for him to feel less disrupted and annoyed. The parent's aim is to control the overall situation from the outset, so that a power struggle is avoided. Therefore, you will find it easier to get along with him if you try to side-step direct battles as much as possible by thinking ahead and smoothing things over so that he doesn't get upset from the beginning.
For example, when it is time to change his diaper, you can manage the situation so that you aren't directly interrupting him when he is in the midst of something he considers very important. Perhaps you can bring the diaper to him and change it while he plays, rather than calling him away and interfering with his interests. Little children are easily distracted from one thing to another. You can use this tendency to guide him, in a friendly way, towards the dinner table or out the door or whatever it is that he needs to be doing. Give him a few moments of preparation by telling him, "We are going to stop in five minutes and put our coats on," so that he is not suddenly surprised by these events. Of course, it takes a bit more time to prepare a toddler for these inevitable interruptions and transitions--but it will help him if you give him this extra time and attention during this phase.
Toddlers are often touchy about everything and difficult to get along with. They have a need to feel in control and in charge and the boss of every little thing. But this normal behavior is usually less trouble if the parent can make the effort to be especially diplomatic and respectful of the toddler's need to feel in control. Toddlers feel pushed around by the same requests that they used to follow gladly when they were younger--the parent often experiences sudden panic when this happens, as if the child who used to be cooperative has overnight become a grouchy opponent. But you can help your son gradually outgrow the "NO!" stage by keeping your cool and side-stepping a direct battle of wills whenever you can.
Elizabeth Berger MD
Child Psychiatrist and author of Raising Kids with Character