Soul, spirit and will
Watchman Nee described humans as "tripartite", consisting of spirit, soul and body.
This is a particular framing of the human condition, a way of thinking about and understanding ourselves. There are many other alternative (or complementary) ways of framing the human psyche: Freudian psychology, Myers-Briggs, the four humors and so on. Their value is in how useful they are, do they help us understand ourselves? Any particular framing may be more or less useful than another, at best they're all approximations of the truth rather than "truth" themselves.
The division of psyche into soul and spirit is an understanding I find genuinely useful. Your spirit is who you really are. You are a living spirit, you have a soul. To understand that things like memories and emotion are part of us, but they don't define us both helps explain who we are and can be freeing. Your memories, your past, don't have to define you - you have memories but they aren't "you". In pyschological speak the soul is closely related to the ego, your conception of who you are and your worldview. They colour your perceptions and shape you, but they aren't you.
Watchman Nee puts "will" as something of the soul. In my search to understand myself and the world (we're so intimately connected to the world - indeed we're the product of the world) I've come to the conclusion that this isn't the most useful understanding.
Will is our capacity (ability) to effect change. I don't think will is a separate thing in itself, it isn't a "region of our soul". The strength of will you can exert in any situation is how much of yourself can you bring to bear on it. How freed are you? So, in fact will is spirit - it's merely a way of describing spirit (who you are) as a force of action (rather than being).
The more natural (more common) situation, and the one faced by us all, is that our spirit is submerged in our soul. Who we are is buried in our habits, routines, memories and aspirations. We tend to live in the past or the future rather than the present. So the task of developing a strong will, a strong capacity for action and change, is to free who we are from the grip of our soul. To divide between soul and spirit.
Tangentially I think a similar thing is true of conscience. Conscience also doesn't seem to be a particular "region" of who we are, but as we are more aware of goodness we will be more sensitive to not doing bad things. Conscience is a description of the right operation of spirit, rather than a thing in itself.
Our daily experience of what we think of as conscience however is likely to be different this. There is a "counterfeit" conscience, a conscience of the soul, which pyschologists call the "super-ego". This is a part of the ego and is your idealised conception of self, the you that you think you ought to be. Guilt and shame often come from the promptings of the super-ego telling us that we're not living up to what we think we should be. Discerning between our real sense of how to live and the prattling of the super-ego is the same task of discerning between soul and spirit, and is the journey of a lifetime.
Talking of spirit raises the interesting question of what is spirituality? In popular opinion it's a word with no real meaning at all, and even amongst Christians there's a very hazy understanding of what it might mean. My current thinking is that spirituality and goodness are two different axes. You can be good without being spiritual and spiritual without being good. Best of all of course is to be both.
Goodness is to love.
Spirituality is self-awareness and understanding (and therefore understanding of the world around us). Spirit is who we are, and spirituality is "of the spirit", so we are more in touch with ourselves we are more "spiritual". There are some outward signs of this, freedom and an ability to flow, that can be superficial and mistaken for a genuine spirituality. As with everything the search is for real depth, in spirit and in truth.
“Each must become God-like and beautiful who cares to see God and Beauty” -- Plotinus