Usually when I make a mistake in my comic and I miss a detail, I actually wait till later to fix it, or I do it on the spot when someone points it out.
Even when you're one of those people that like to double check everything, sometimes it just misses the eye and OOPS YA FRIGGED UP.
I constantly do that and to be honest I think it's just, for some of us, we have so much fun drawing our stuff we tend to miss little details due to our excitement.
At least, thats what it feels like to me |D;;