['The other week, I was talking about a co-working of mine - okay, I was gossiping..', 'Hmm, how did that make you feel', 'Pretty awful, actually.  Especially considering that the coworker of whom I was speaking was in a room just next door with the door open.']
Yeah, at least now you're more aware, it can be pretty tough when you're trying to break the habit though
I once was talking about a coworker behind his back.  It wasn't necessarily an awful conversation; but what I didn't know was that he was working in the next room with the door open.  He approached and asked what I had been saying.  I knew I was caught.  I was so disgusted with myself.