But sometimes I forget or get lazy or start speaking too quickly or whatever.
The French equivalent of putting your foot in your mouth is mettre les pieds dans le plat. To put your feet in the dish, although originally plat referred to low still waters and not food.
So at a dinner party recently, when I mentioned that I had a habit of putting my foot in my mouth, the guy sitting next to me looked at me with the oddest expression on his face. Clearly trying to gauge how flexible I would have to be in order to have such a habit or how clean I would have to keep my feet in order to have such a habit. He looked a little disappointed when he realized that I only put my feet in dishes and/or low still waters.