I know I'm super late to this party, but I just had a similar instance today. We were working on iai and I misjudged the timing, and so felt rushed to catch up by engaging muscles to try and speed up. I know this is not our way, so I relaxed, focused on moving my body and not worry about what the opponent was doing. Things suddenly work well. I'm no longer surprised it works, but I am still slightly surprised by how easy it becomes and how little I need to do. I know when we run into a lot of mass or strength, the reaction is to engage muscles to overcome or at least attempt to balance out the forces. This is where letting it go comes into practice, in a lot of ways. Be unbothered....I like that. Imma steal it. 😁