I just coined a phrase that sounds like it belongs in this thread.
Recently I was sitting, 'engineering' on the latest build when my wife came out to the shop and asked me to help her move some furniture. We had taken the Christmas tree down and she decided to rearrange the living room. I tried not to show it but her request came at a most inopportune time. I had a concept in my mind, was mentally working out the details then had to stop and leave the project to go do her bidding.
I decided that she had broken my 'Mental Momentum'. By the time I got back to the shop I'd lost my train of thought and had to start over. I retrieved the thought thread but it took a while. My 'Mental Momentum' had been interrupted.