special treatment

I hate when you have to discipline one kid what seems like all the time and rarely the other kid.  It feels as though one is getting special treatment, but she is not.  It is just that one tests and pushes the limits and is often in trouble.  Still, I feel terrible and wish she would just make better choices and try to keep her anger from exploding out of control.  I want nothing more than to be fair and treat all my kids the same.