I've spent countless hours trying to pin down all prime faculties of consciousness. I'm at six right now and almost everything is explained; the remaining things I don't understand are facets of these.
The person can "choose" between their own happiness and their conscience when the two come into conflict, such that multiple choices are possible without any difference in precedent.
The person can be given "perceptions" as a direct result of external events. These perceptions can be pleasant, unpleasant, or neutral.
Conscience is the person's inherent sense of the "morality" of an action they could take in their current situation.
Certain types of events trigger pleasant or unpleasant experiences. The defining difference between emotion and perception is that emotions depend on beliefs instead of coming directly from external events. There also aren't any neutral ones. Emotions can also be triggered by Instinct or in some ways by Imagination (that's one of the biggest areas I don't understand).
The person has an internal system of associations built by experience that causes them to automatically feel certain emotions, believe certain things, or take physical actions without making a choice, when the associated trigger is experienced.
This is why sometimes you can't stop yourself from reasoning. Instinct isn't controlled by choice. Imagination mostly is, but you aren't guaranteed a victory when you try to fight your Instinct that way.
I should mention that "intuition" as an epistemic source is based on instinct. And it does have weight. If you feel something "should" be true but can't explain why, it's because your Instinct has learned from real experience to associate that belief with some other beliefs you have at the moment. You can't tell which ones from this alone, but that does constitute a reason to believe it as much as (a weaker version of) AlphaGo telling you a move is good or bad even though you can't see why.
Phobias are also based on Instinct. Specifically they're intense assocations caused by traumatic experiences (I have one strong phobia and I can trace it to a very traumatic experience I had when I was 4 or so). They self-perpetuate because seeing it and being scared of it reinforces the association.
Even memory is, I'm pretty sure, a function of Instinct. Having or imagining a related experience - or just one temporally close - calls back an old experience into the Imagination. Memory being a facet of Instinct helps explain why memories can be corrupted or forgotten, and why you can sometimes be unable to remember one but it's not completely gone; going back to the place it happened in or hearing someone describe it might bring it back. In fact I suspect that no memory is ever completely lost.
The wikipedia article on "flashbulb memories" is the pinnacle of uninsightful. It's obvious that an experience that means a lot to the subject will be remembered more strongly. That's not some kind of unsolved mystery. As for why some memories that don't seem at all outstanding sometimes get preserved this way, I'm pretty sure that's just happenstance: if for whatever reason you end up thinking about an ordinary experience a while after it, you're strengthening it by calling it back (creating another memory about it), which of course makes you more likely to remember it again at some point. If this happens several times to the same memory, it's no wonder it ends up the only one from the time period to be preserved years later.
By the way, I think I know why we don't remember our infancy: because we didn't have language. It seems to be that memory is bad at storing plain thoughts, so it's much easier to remember if we have a way to encode those thoughts into Perceptions (language encodes it to audio).
It may also be related to that our picture of the world and of ourselves has evolved so much since then that the things we used to think about just don't have any meaning anymore.
You know how when you forget something you were thinking about it can be really annoying as you try desperately to get back a thought that must be in your mind somewhere, and it just won't come? That process of trying to remember is actually done by trying random thoughts that might be related in the hopes that one of them triggers the lost thought through Instinct. And the thoughts you try are themselves suggested by Instinct. Once I understood this, I got a lot better at remembering things, because I could control the process consciously and take a more rational approach to it instead of agonizing and hoping my Instinct does it for me. When this happens to me I go through the thoughts and conversation that I know led me to the thought in the first place and it almost always brings it back in short order.
I even think beliefs are reducible to Instinct. Here's a question: what percent sure are you that (insert any belief)?
You probably can't say exactly. If you can, pick a belief that isn't 100% or 0% and that isn't anchored to quantified information you have (like the outcome of rolling a die), and I know you'll see it: we aren't certain exactly how sure we are of our beliefs. Even by thinking about it we can't pin down a number. So what's happening?
The number you're looking for doesn't exist. The definition of belief is: I believe X <==> if in a situation where I could act such that if I were right about X I would benefit and if I were wrong about X I would lose equally, lacking any other factors, I'd act as if X were true (I'd experience a temptation to act on X proportional to the certainty of my belief).
With that in mind, it's clear that until it's actually tested, your degree of certainty isn't stored anywhere. The only reason you can tell that you "believe" it at all is that when you wonder whether you believe it, you're really asking your Instinct whether you'd act on it if you were in the situation. Instinct, of course, doesn't have a consciously-viewable percent certainty, it's just a predictive web of assocations that can usually tell how you'll act because it's so experienced with you.
If you're one of those people who says things like "I'm 99% sure that free will exists, but I can't be truly certain because I haven't perfectly ruled out the possibility that it's an illusion", this is why you should stop that. If you'd always act as if X is true, then you're certain that X is true. So don't hedge your statement.
A person can "imagine" an experience, and if this experience would trigger an Emotion, a diminished version of it is felt (this effect seems to be the basis of fiction, though there's still a lot I don't understand about it).
It might sound crazy, but Imagination is actually how we reason. You get a belief from Instinct via the above process and it goes in your Imagination, and having it there will make your Instinct jump to a belief that you think is entailed, replacing the one in your Imagination and delegating the previous thought to memory. At first - when we're infants - the whole process is controlled by Instinct: we start by having some Perceptions and then Instinct learns to predict them based on that (ie. gives you beliefs about what will happen in a given situation). After a couple years of experience, the person gains a conscious understanding of logic (storing some emergent principles, such as the contrapositive rule) and then can reason objectively instead of being filtered through the lens of their partial experience.
This came about from me trying to pin down all the fundamental rules of logic. I eventually realized that there's only one: non-contradiction. All there is to valid reasoning is understanding what a statement actually means, so you can tell whether X actually contradicts Y or not; and having enough extrapolated rules stored in your Instinct to consider a complex scenario in a reasonable time frame (and not having any false ones).
An advanced version of this use is to play out hypothetical scenarios to predict things, or invent stories.