Let me explain. If Spinoza's is the sword that beheads the king of moral relativity, Aristotle's are the tools that till the soil afterward. Spinoza crafted a beautiful argument for the fundamental virtue that all other ethics can build from. Aristotle engaged in practical theorizing about individuals (particular virtues, rational thought, human excellence) and groups (forms of government, proper political engagement). One of Aristotle's tools was the
Doctrine of the Mean: "every virtue is a state that lies between two vices, one of excess and the other of deficiency." To be a courageous person is to be the proper distance between a cowardly person (deficiency) and a reckless/impetuous person (excess). To be "properly cooperative" (I don't know a better word) you must be the proper distance between a scrooge (deficiency) and an altruistic fool (excess).
We must continually exert effort to keep ourselves in the fertile valley nestled between deficiency and excess. In that sense self-improvement is a continual and unending process that we engage in for our entire lives, analogous with eating healthy and working out.
Take your example of the business owner. He might be able to entertain any number of possibilities for enhancing his business and he must continually strive to be virtuous (act with integrity, courage, proper cooperation, etc.) in his business so that he makes the best product possible given his goals, fosters the proper relationships with his clients (and/or suppliers), and so on—but these things are
means between vices. He must exert the proper amount of effort to act with integrity, and then no more—for any further and he strays into excess. After a certain point expending more energy is not useful. Outside of this analogy, money has diminishing utility as we acquire more of it. A certain amount lets us purchase the things we need (shelter, food, etc.) and a certain amount more allows us to be comfortable in the pursuit of our hobbies, but there is a point where more money does not help you acquire the things you need or can reasonably want, and so spending time acquiring that money is
excessive. It is an example of a vice (greed).
In other words, we have to continually maintain the proper amount of power so that we can affect our internal and external reality
to the extent that affecting it is useful to us.
The practical consequence of this is that someone who is vicious (cowardly, cruel, lacking a sense of justice, etc.) will have to spend a lot more time and effort moving themselves to the means between deficiency and excess. In your words, I think, they will have to dedicate a lot more of their time to the acquisition of power; their inner character is equivalent to that of a person in poverty who cannot afford for their own basic needs, let alone the things they want.
Aristotelian virtues are habits, or ways of being, not singular actions. To be a courageous person is to be
naturally inclined to act courageously due to an internalized rule of behavior. It is to always be drifting toward the mean between vices. This frees a courageous person up to occupy their mind with other things, as they do not, in typical everyday circumstances, need to
exert a large amount of effort to be courageous. Though, of course, there are more or less trying circumstances even for properly courageous people. In any case, once you are naturally inclined to act courageously, you ought to expend the effort required to maintain that (e.g. not to allow yourself to entertain cowardly desires or to act on those desires) and no more.