I take good care of my teeth, but my dentist thinks I don't?!

I used to only take OK care of my teeth. I would only floss every once in a while and sometimes rush through brushing. Despite this, my dentist would always tell me what an amazing job i was doing. For the past 8 months or so, I have been doing much better: taking great care of my teeth. When I went to the dentist today, she seemed to think I wasn't caring for my teeth at all. Could there be a good reason for this? On top of being really annoying, I'm wondering if there's something wrong.