In my experience, the three businesses merge and trickle into each other.
My business is often influenced, at a subtle level, by the business of others (i.e. their expectations of me, which part of myself I want to show to them, how I want to be perceived, what they think I must be doing etc)
This is seriously tricky, because then it is your business disguised as mine in some strange way. It is not truly mine.
As I was reflecting today morning, I discovered that truly my business (to use the language of this piece) was nothing exciting at all. It was just small things, normal things.
And so much of my ambition, my desire to do things, to change the world, to influence, to experience were all driven by the other two businesses trickling into mine (and then seeming to be mine).
Truly staying in my own business also means coming to terms with what that business truly is - and it may not be what you thought it is supposed to be, or what it was meant to be. It may just be some very very simple and small stuff.