Back when I was active professionally in photography a consistent problem I had was remembering whether or not I had advanced the film and cocked the shutter. As a result I would often point the camera down and press the release. About 50% of the time nothing would happen and I would then advance the film and take the picture. The rest of the times I would end up with an out of focus image of my foot.
At one point I tried turning the camera toward my face and looking but after temporarily blinding myself when the strobe went off right in front of my eyes I returned to collecting more photos of my foot.
It’s a habit I never have conquered. Even with digital cameras I still end up with images of my foot quite often.