I had to develop new habits for digital cameras: with film if I have to set down an empty camera which has a strap on it, I'd leave a rewind button raised, etc. Habits, habits, habits, that's how I've always gotten by, especially if you've any tendency to be absentminded or forgetful.
(Also, having a grip on my K20d most of the time is nice, apart from adding steadiness for me, it means my sweetie doesn't have to wait while I'm dithering about being sure there are spares in whatever bag I'm using that day when we rush out the door.
)
These days, when a digital is empty of card or battery for any reason, I turn camera upside down. I could leave the door open, I suppose, but that is potentially dust-inviting.