Because I say it all the time, that's why. I think of it as a positive affirmation. As in, "I am NOT crazy -- I know I put my keys right here!" Or, "I am not CRAZY -- I just saw a velociraptor in the bushes!"
And apparently, I say it enough that my kids have picked it up. Like, at church, when I asked G-Dog to please be quiet and sit down in the pew, he yelled (no exaggeration here), "I'm not crazy, Mommy!" And so, now that I have joined the 21st century and started a blog, I could think of no more appropriate title than the thing I tell myself to keep from checking right on into the loony bin. Now, there's a record. I am officially NOT CRAZY!