My hot-headed loner geek who is living with his father and a houseful of roomies is the most miserable sim in my game. He also has the domestic personality trait (from family aspiration). He will occasionally, and suddenly brighten up, but most times I find him glowering outside bathrooms, setting himself on fire, or trembling with tension. When first created he refused to enter his own house due to stranger danger.
Despite all this he still has managed to make himself one friend (not a housemate, or his Father) Maybe the game felt sorry for him, or maybe I clicked on the wrong sim at some point.
He is currently sitting by himself in a darkened lounge, staring at an 'off' tv & thinking about whisks.

Other loners seem to behave slightly differently depending on the combination of traits, and most likely whether their loving controller forgot to introduce them to their house mates, or not. oops

But surely sims are capable of introducing themselves to their own household members? I mean sublime to ridiculous - in TS3 if you made them one household they acted like they'd always known each other. Now they act like they never will unless you do it for them.

So it's a matter of tuning? I agree it would be a less than satisfactory result for outgoing friendly sims but I haven't tried that.
This sim just seemed to suggest this path.
It turns out that the sim's father had in fact died of old age and was not eating his way through four plates of cheese sandwiches, as I had left him when taking another household member out to mess with the telescope on community lot.
So funnily enough, sitting in the dark with the tv off was not that unrealistic, especially as he never hit it off with his dad. Regrets?

With the sims 3 tuning I would have needed to make him fall out with everyone to get this result? In fact for this sim, this tuning seems to work. I'm finding there are definitely scenarios that don't work for me (would they work for someone else..I don't know?) Sims / households get deleted in CAS because at some level they don't appeal to me.

This sim feels significant and memorable, and I am affected by him, sometimes amused, other times frustrated. If you add to that that his personality is based on a real person, and I had a big ding-dong row with him just after his father died I do wonder how much of our interactions with, and reactions to this game are wholly conscious.

My loner sim will get the tense moodlet - it's just she's got like 5 other things happening that boost "happy", and half the time I can't even tell she has the tense moodlet unless I expand the moodlets. It does not actually change her mood. It doesn't make her stop going into the living room where all the strangers are, and talking to her children (and the strangers). I may take initiative and move her out of the room because I expanded the moodlets and noticed she's tense. But she won't do it herself. That's what I mean by VIEWING it as just a way to get whims. Not that she doesn't get the moodlets, but that they don't make a difference in her behavior/personality.

Fact is that the +1 tense cannot overwhelm the +6 happy she's got going on 95% of the time, and so my opinion is that it doesn't feel like she's a loner. What I wish is that things like loner, or hot-headed, or gloomy, etc, gave something like a +6 boost to their respective emotions, so that it can actually overpower the happy moodlets, and it'll feel to me like they have an impact on something other than whims. I even have Zerbu's uncomfortable changes mod in, but unfortunately that only works if the loner has the tense moodlet AND she really needs to pee/eat/sleep/etc.

I'm sure there's plenty of room for improvement, but my opinion is that I've observed the opposite. Granted, it's been long enough that I've played Sims 2 that I'm a bit hazy on comparing 4 to 2, but I've found sims in Sims 4 are considerably more interested in autonomously socializing with each other than Sims 3. Mine are always chatting with each other, even while they're eating, watching TV, or using the computer. In TS3, I couldn't keep two sims talking unless I stacked their queues with social interactions. If I let them be, they seemed very indifferent and would wander off. So I think overall, TS4 is quite a bit improved in that area. A few things I would improve are sims don't wander off unless whoever they're talking to stops talking. I've noticed the target sim will sometimes just wander off, but the speaker keeps speaking as though they didn't notice. Or maybe if you force a sim to wander off by canceling the action, the speaker will notice and say, "UH!" and make a gesture like they think the other sim is very rude. Also, a sim will be in the middle of a conversation and then suddenly want to play with their smartphone. Very annoying, and very rude.

I haven't really noticed loyalty being any worse than TS3 either. It was always possible in TS3 to whittle down the defenses of committed sims and get them to cheat if you worked at it. TS4 don't seem any less loyal to me. In fact, I've found it does take a good bit of effort to get a committed sim to cheat. I have a married sim who refuses anyone else's advances if they didn't have a pre-existing high romance with her. I haven't noticed any autonomous propensity for cheating either, at least, not if they didn't already have high romance together. I've seen autonomous cheating, but I'd turned that sim into a cheater by building up his romance with several mistresses. I think if you don't want sims that cheat, it's as easy as not turning them into cheaters by building up romance with others.

@brytewolf What kind of environment are you playing your sim in? One of my houses is almost completely composed of burnt out furniture, and the gloomy artistic sim who lives there seems to be more half and half than -1 +6. I'm not suggesting that as a playing strategy, but I wonder if there might be a modding solution which brings down the environment for certain sims only.

Sounds to me like you're just taking good care of her

She does have a really nice house I downloaded, so it's always "nicely decorated" (and the comfortable one, and oh, I slept so well cause my bed is awesome!) and then there's usually several from either good conversations, or good woohoo, or having such a wonderful child or...you get the picture

I would love a modding solution to this. SO MUCH. I like the modern houses, so that's always the upgraded furniture, etc, and then it's IMPOSSIBLE to make her unhappy!! And I want to have them experience their personality traits, gosh darn it!! lol

You think she'd be grateful and give me what I want every once in a while (an unhappy mood!) but NOOO

I like to view it as that is just an underlay emotion. I'm a bit of a loner and being around people makes me tense/nervous but if i'm happy enough then it kinda just gets pushed aside. It's still there it's just not on my mind as much. But yeah i wish that the emotion/moodlet that correspond to a trait would have a greater effect on my sim but thats why there are mods

If you want your Sim to keep acting according to original traits you should keep him or her in a starter house with all that cheap furniture and appliances and absolutely no aura emitting or decorative objects. I have a genius/geek/tense programmer whom I deliberately kept in such a house, just to see what would happen, and it worked. She was tense most of the time and not only tense but mad as hell every time when she returned from her job. Then she would play games on her PC for a while and become content but as soon she got up she was, more often than not, tense again. After a while I added some objects that she had earned, like the hard drive, and even enabled their aura; she would become focused for a while but nothing really changed.

... however ...

Somehow she got involved with Zoe from The Roomies household - that's what comes out of saturday night fever. Now Zoe is as horny as possible (there's no other word to describe her) and she makes my Sim horny as well; they just can't keep their hands off each other. My Sim still gets hungry, etc., but once her basic needs are satisfied she is at least happy and I've never seen her tense again since Zoe moved in.

So it seems that, at least for now, objects do change Sims' emotions but only other Sims can change them a lot - and there's no way around it, unless you make your Sim a real hermit. As far as I am concerned this is as it should be; I just hope they won't spoil it.

Wow...that almost describes me. I don't come home angry, but really stressed and playing at the computer makes me happy. As soon as I stop, I feel stressed again. Maybe I need new things? Oh, but we're talking about Sims....