Even when doing a mock radio show that won't be on the air, it's best not to be too self-deprecating. I remember a broadcasting school instructor stopping a student's tape after her first song intro.
"The morning guys had a great show, but I'm here now," the aspiring DJ said over her first song.
"Don't undersell yourself that way," the instructor told her. "Don't put the idea in the listener's mind that your show won't be as good as the one that just ended."
That's sound advice--for radio and life.