When my son was born he was the most mellow and easy going baby. He didn't cry much, was always smiling, and was content just hanging out. (He didn't sleep, but I think that is just the curse of my kids). He's now 15 months old and it's like he's had a personality change. He's still happy as can be and always smiling at family and strangers alike, but he has this stubborn streak that has started to rear its ugly head.
He fights me to the death when I change his diapers or clothes. I'm talking horrible battles where he screams, holds his breath, turns purple, and tries to escape. He throws horrible tantrums if his sister takes a toy away. He gets his feelings hurt and breaks into tears if anyone says, "no" to him, which lately he has been told a lot. As in, "No, you cannot climb into the toilet." Or, "No, you cannot walk in the street without holding my hand." Or, "No, you can't hit your sister in the head with that stick."
I know he is just asserting his newfound sense of independence, but man it is frustrating and exhausting. He went from the world's easiest baby to the world's most exhausting toddler.