Concepts, in my view, are a better approach than treating things as though they are written in stone and Sensei did often talk about the 'Formless Form' that came with deeper understanding.
The term 'Kuzushi' means to imbalance and can be an art unto itself, simply studying how to imbalance an opponent in various ways seems to be the basis for Arts such as Judo, Aikido, and Jujutsu, but people tend to focus solely on the physical aspects of imbalance.
When we train we must understand how the mind can be knocked off balance and work to defend against these things, not just in the Dojo, or on the Street, but in everything we do.
We used to play a game at the old Bremerton Dojo where we would look for openings and 'cut' the other person in an effort to teach a lesson about not leaving oneself open in that way.
These were meant to teach us attention to detail and never to become lazy in our actions, to always focus, to always be ready for whatever may come and to never... Ever... EVER lose our One Point.
Of course there are some great physical drills for this sort of training, one should spend a lot of time doing Kakie in various forms along with other Kuzushi drills and apply Kuzushi from Kata to seek a deeper understanding.
These are traditional, another way is to get a partner and simply practice pushing and pulling in various ways with a mind to feel and develop sensitivity... Not just to merely push or pull an opponent, but with a mind to feel their center in conjunction with your own in order to displace it, which is far more effective than merely pushing or pulling without such a focus.
From there one can move to a less static drill, having the opponent actively come at you or pull you as you counter the movement based on said sensitivity.
As you go on you will be able to see how a simple thing like talking or lightly touching the wrist can disrupt the opponents' mind as though you have moved a Mountain with your Pinkey Finger.
Apply this to stressful situation you may encounter throughout the day or the week as you go to work or even in your off time and the sensitivity works wonders at helping you to maintain that One Point, effectively countering any attempted mental disruptions and stress with ease.
Leave no openings and do not be lazy in your stance, but anchor in your center in all things...