You get that diaper changed and try to take off his pajama shirt, only to meet with a struggle. For a lot of parents it seems that 'mine' is one of the first words their new talker learns. It's not really, but it can feel like it. I know that on a daily basis I wish that word was not a part of my son's vocabulary. However if you keep in mind that your child is going through a natural stage that will enable him to develop his moral character and how you handle this irritating word can make a big a difference.
Toddlers view the world through a self-centered looking glass.
They simply do not understand the complexities of life. To them they exist, their Parents and Caregivers exist, siblings and a few little friends exist. What they do understand is what they want and how they feel. They simply do not have the internal skills to understand how the other person feels. That's why they don't understand why in the world they have to share that toy with brother or sister, they can't eat the whole box of ice cream for breakfast or why you're making them change clothes when they really like that pajama top.