When did I become so Assertive?

Recently, I became a Charge nurse. One that other nurses look to as a resource for answers based on my nursing experience and policies and procedures. When did I become that person who is the cutthroat decision maker and the one who has the guts to call the Dr. and TELL him/her what the patient needs rather than asking. Whereas, when I was a new nurse I was very timid like most good nurses are at the beginning but I was timid outside of work too.
When did I transition from the person who always held my tongue to the person who can't keep her thoughts and frustration to herself?

For Example:

Tonight there was a patient (a child). Maybe 5 or 6 years old who threw tantrums by screaming and throwing things off his bed because he wanted his mother to come back with his game. His mother never shows so he continues with the screaming for hours and regresses by peeing in his bed. Of course he is way too old to be peein' in the bed now.

Since I couldn't pop the boy, I had to be verbally forceful with him and threatened to take away his video game console if he didn't stop with his outbursts. So I pushed it away because he wouldn't stop. After taking it away, he continued for a little longer but sooner than later stopped.
I felt like a mother. I should not have been this boy's mother. Where is his real one?

I digress. When I was a new nurse, I would have been shocked at this kid's behavior and just stood there quiet and stumped. Speechless and unable to process my thoughts on what I should say to him to make him shut up.

On the same note.. I can turn around and be sweet and still get nice ones to follow instructions. I swear I'm not bipolar.