My body has some interesting ways of telling me that I am too tired and need some rest. I start missing things. For example, I might walk through a doorway and bang my arm on the door frame. I actually miss the opening! Or I may try to set my keys on the dresser and miss the dresser, dropping them on the floor. Or I will enter a room and try to flip on the light switch, missing it several times before finally connecting.
I usually just laugh at myself when something like this happens. What else can you do? But I also try to acknowledge that my brain is trying to tell me something, and I need to pay attention.
So if you reach into the refrigerator to grab a carton of milk, and knock three things over as you recoil your arm, you probably need a nap. The sooner, the better. Before you do any real damage.