Following the Non-Duality understanding, it's important to recognise that we are not the doer and we are not the thinker. Actions are part of the flow of the world, and thoughts are also activity flowing with the world. We are not this. We perceive the flow of thoughts and actions.
There is a sense of 'I am this' that is thought based but pervades the body and its actions. There is a sense of 'I am this body'. There is a belief that 'I choose', but all choices made are influenced by the world, so free will is not as free as it seems to be. What we perceive is a sense of 'I am this' thinking, choosing and doing. But it is not accurate.
Firstly 'I am this body' is too vague a definition. It cannot be said accurately where the body begins and ends. The reason for this is that the body doesn't begin or end. It is a flowing 'part' of the world. It continually changes and breathes with the flowing nature of the apparent world. So really the body is infinite. That ultimately means there is no body. What we consider to be a 'body' is a vague idea of a limited form in an infinite indivisible universe. The idea of separate forms is useful but not accurate.
Secondly, we cannot be what we perceive. We perceive the body and its actions. We are not it. We perceive thoughts and the sense of identity. We are not this. This is where Detachment comes in. In spiritual practice we recognise that we are not anything that we can perceive. We are perceiving. The eye cannot see the eye, and deeper still: Awareness cannot perceive itself directly. Yet all that is perceived is nothing other than Awareness. The world appears within Awareness, but Awareness is not defined or limited by it.
So the Detachment we seek is a letting go of identity. This is not for us, this is for the human mind and the false sense of identity. We perceive the thoughts and the sense of identity trying through spiritual practice to achieve enlightenment, nirvana, or self-realisation. The false sense of self is trying to free itself from its confines of identity and be who we really are. But we are right here, perceiving this play of identity, the play of limitation and freedom.
The practice for the body-mind is to release itself from its limitations and just be. So it is a letting go of identity with thinking and doing. We do not think or do. We perceive this. Perceiving, or rather, Being Aware, is the natural state. It isn't a doing. It is the natural state of simply being. The world appears in this. The sense of self rises and falls in this. The practice is to just be aware and not get caught up in the plays and drama of the world.
It doesn't mean that the mind and body should distance itself from the world, shut itself away. It doesn't mean that the body-mind should give away all belongings. It doesn't mean that the body-mind abandons friendships and loved ones. It is more that the mind recognises there is only One, an Infinite Indivisible One. So we cannot be this or that. There is no-one other than the One. So the body-mind gradually changes so that its thoughts and actions fall into line with this deepening understanding of Oneness.
Ultimately, of course, the sense of separate self will fade away as the belief of limitation evaporates. It doesn't mean that there is a huge change. We are here all along. It just means that the selfish identity no longer gets in the way. There is an improved clarity between the true Selfless Self and the body-mind through which it is expressed in the world.