Growing pains

Is it just me or do all children put their parents through "h, e, double hockey sticks"?  Currently, our children are 7 and 4.  My 7 yr old does give me fits from time to time but all in all he's a really good kid.  My 4 yr old on the other hand is a totally different story!  She is driving me crazy right now.  I don't know if it's a phase or what but she has gotten so sassy and smarty acting, I just want to whip her little tail when she starts that mess.  Is it just me?  Am I over reacting?  I could understand this attitude if she were, say 10 yrs old, but 4?  C'mon!  Am I wrong to feel this way?  I feel like she MIGHT grow out of it but then again, what if she DOESN'T!  Oh, dear...