Nothing will call your attention to this very moment---fully integrating your mind and your body, knocking you completely out of any thought loop---faster and more completely than having the shit kicked out of you.
The Aikido version of all of this is facing that guy screaming fiercely from the bottom of his belly, swinging that big slab of hardwood at your skull, or facing a handful of thugs rushing at you from the other side of the mats, coming to take you out, with you just trying to survive for a maybe a minute... These are the opportunities to practice this same flavor of spirituality: We practice finding and operating from a place of peace and harmony within these chaotic situations. Eventually, we may even begin to realize at a very deep level (vice intellectual understanding) that these dojo situations are analogous to other situations in our lives.
These situations will knock the mu out of whatever you think mushin means, leaving you with the real deal. That's when you'll truly know spirituality.