The Push Back

As my son is getting older I have noticed some behavior that I thought would occur only in the teenage years.  The latest scenario is he asks to do something and I tell him no.  Then he proceeds to tell me he is doing it anyway.  We have been having a real problem with listening lately and an abundance of time outs.  Is 5 going into 6 the big push back age?  Trying to establish their independence?  In this house it is and it is driving me insane.

They say that by 6 most behaviors are harder to change in a child they are more moldable before this point and that makes me a little scared.  Have I not done my job properly as a parent?  Is this a behavior that is here to stay?

I want my child to be strong willed in general in life but not so stubborn that he can't react properly in his normal life.  Plus when he reacts this way he sounds like a spoiled willful child that doesn't respect authority which is definitely not what I want.  It is a crazy balance trying to ensure that your child has just the right mix of both.  We are making progress slowly but it is proving to be harder that I could ever have anticipated.