I'm not gonna get this right holistically. But it's important to get this down. It's a framework put in production long enough that it needs to be formalized here.
Let's start with some ideas you're already familiar with.
There's the parable of the two wolves and the one you feed.
Shyamalan's Split is one among many movies that depicts a person with multiple personalities.
If you're academic inclined there's also the concept of subselves.
I no longer take these as fiction. I'd like to propose a mental model: that are more than one "you". What you think of as you in fact is a collection of different personalities. Pixar's Inside Out made a good showcase of that but accurate enough only for child.
I call these internal personalities prototypes.
Think of a prototype as an almost complete person. What sets a prototype apart from other personalities within is his value system. In that a prototype will have a sense of what are important. For instance I have a prototype who value solving problems; and another who has a strong preference for order over chaos.
Trouble comes when two or more prototypes have competing agendas. When your internal ecosystem is developed enough, it's pretty easy to imagine two prototypes with contradicting value systems.
Suppose one prototype of yours is deeply fillial. But another prototype is ambitious. There is now a great career opportunity far away and you cannot bring your ailing mother along. No matter which choice you pick, one prototype will be resentful.
Take another group of people stranded on an island. They come across another group that need the limited food available. One person is interest to protect the survivability of the group, he chooses to not help. Another person feels intensely compassionate, she chooses to help.
These two are in conflict and effectively paralyzes the entire group from moving forward. All these can and do exist within a person. Without a sense of mastery (integrating two opposing truths) the person is only capable of making bad or worse choices.
On a moment to moment basis, only one prototype gets to drive your body and mind, largely speaking. It will be a problem if one or two dominate the wheel all of the time and other prototypes only get to watch. Think of this as parts of you that do not get to express.
The last thing I'll say about prototypes here is: the more you learn and grow, the more value systems, desires and habits you're gonna pick up. Over time, more prototypes emerge. I would imagine an average 18 year-old to have about 3 prototypes; a 35 year-old would have 6 or more.
More isn't better, neither is less. Who you have is who you have.
"You are your own worst enemy" now takes on a different, literal meaning.
When I started this I intended to put down everything I know in one post. I'm afraid that's no longer feasible. In the next section we're gonna look at why all of these matters.