Defiance is the way that a preschool child asserts himself. He wants to show the world that he has his own identity and is not as dependent on you as he once was. With this newfound independence, he will begin to ignore your demands, especially when you tell him, "no".
Most of the time, parents will use the word 'no' too often and it begins to not have any effect on a child.
Make it positive. Think before you automatically say no to your child. Is there a way that I can rephrase my response so that I am not using the word ‘no’? A two year old will respond better to a direct positive instruction. For instance, instead of saying, “No, don’t play ball in the kitchen,” say, “Let’s go outdoors to play with the ball.” Instead of saying, “No, you have to hold my hand in the car park,” say, “I want you to hold my hand because the car park is dangerous”.
It’s also helpful to offer options when you need to say ‘no’ to your child. As an example, if your child wants chocolate but you don’t want her to have it because it is too close to dinner time, offer alternative healthy snack like grapes, instead of a just denying her request for chocolate. This allows your child to make a decision, and making decisions helps a child feel in control.
Distracting your child’s attention from something that would cause you to say ‘no’ works as well. If you’re shopping and your toddler reaches for a glass jar on the shelf, move her away from the jar and divert her attention to something else in the store. This is much easier than saying ‘no’ over and over.
Lastly, choose your battles wisely. You don’t have to say 'no’ to everything. If your child wants to splash in a puddle while walking home from the park, let her. As long as there is no harm in doing so, why not indulge their sense of adventure?