It seems that some days I can be in the zone and other days I'm not. Some days my hands know exactly what to do and other days they fumble and hesitate and don't make very good choices. They can pick up several stones before they discover the right one to go in the next space in the wall. This is not very efficient. It is also frustrating. Often being out of the zone is a matter of being too crowded. If the stones you are using are too near the wall there is no room to work. If all the stones you have to choose from are all piled up on top of each other this makes for awkward working conditions too. Sometimes the ambient noise is distracting. Music can put you out of the zone as often as it can glide you into it. Ironically 'rock music' is not always the best music for working to. Weather is sometimes a factor. However cold wet weather isn't always a problem and one can be 'in the zone' in the most adverse conditions. Conversely one can be out of the zone when absolutely all the working conditions are ideal.
If I feel like I am getting out of the zone I usually do a lot of the hearting for a while. Taking time to just place the filler stones until you get back in your stride seems to work. Your eyes and hands mull over the material available to you and the spaces that still need filling while you are hearting and you get a much better feel for the types of shapes available. Slowing down helps too. If you are trying to rush (rather than going with the flow) it's as though the stones purposely work against you.
I think of walling like surfing. You have to wait for the big waves. You cant make them happen. And then when you get in front of a good one, you paddle like crazy and then ride it out.
My helper admitted he was out of the zone all day today. He was quiet and persevered but it was obvious I had a better day productively. We joked about it. We agreed it would be good if you knew ahead of time if you were going to be 'out-of-the-zone' the entire day. Then you could just skip going to build walls altogether and go do something else that day (like surfing on the internet instead).