Personally My take on this is a little different.
I am an intravert. I take relaxation by being alone, for me people, even the best of individuals are work, for all there are things i can get out of being with another person that I can't get from being alone.
Because of this, even when I'm living with others (as now when I'm temporarily at my parents), I spend a lot of time by myself, because I simply find my own company easier to take.
Whether this is the same if you have a significant other whome you life with I don't know. A friend of mine, also a confirmed intravert said not but I've no experience of that so I'm not sure, though i do admit I don't find my dog half the same trouble as I would find another person and I am quite happy being with her! even at points when i couldn't stand being with other humans.
the problem however, is that isolation is like any adictive pleasureable thing. When you combine it with abuse, it's often easier to isolate than to take the work to get what you need from the presence of others. I've very much been in this position myself, indeed there have been points I have not spoken to another human or even left my flat for four or five days straight.
This is when isolation becomes unhealthy, when a natural desire which would usually only be expressed by say being alone for several hours a day is expressed by being totally cut off from all human contact.
the only cure to this is recognition. for myself this meant making weekly commitments to leasure activities where I would see other people, also I will admit having a dog helps hugely, since quite often what I won't do for myself I will! do for her, indeed the fact that reever is a guide dog and thus actively needs to practice her skills at guiding each day mean that I physically can't! avoid say going shopping, (indeed where I used to only go shopping early in the morning when things were quiet to avoid the crowds, now I go at the busiest time just because! reever loves making her way around large crowds of people).
Of course, this is only individual contact, perhaps with a couple of friends.
I'm afraid I disagree entirely with justplainme. "a functioning member of society?" well why should I care about society! it was society! who sent me to the school where I was abused, heck, it was the "Society" of that school who gang raped me there, and it's society! who mean I have to develope amazing skills at communication just to be recognized as a member of species homo sapiens because I have a visual imparement. This indeed is part of my reluctance and why making those weekly commitments to see people at group activities are so difficult.
if I walked into a pub right now, nobody would speak to me, indeed I used to test this as an undergraduate, going to the colidge bar and just waiting for hours. The only way I can get people to even recognize that I'm human is by having a situation where people are forced! to engage with me, eg, a choire roleplay session or other hobby related activity, and then employing social skills.
Frankly "going out" or "partying" are pretty alien concepts to me, about the best interaction I can ever get with someone is individual conversation, and to get to that point takes a lot of work.
I hate society! much as I don't particularly hate individuals, indeed for me at least, the single worst force of human nature is people's ability to band together into groups and lose what makes them human in all following the same trend, obeying the same rules, and (as usually happens), excluding the same outsiders.
I remember a Doctor who story in which everyone lived in individual apartments only reachable by teleportation, and the teleporters only allowed three people in one room at a time. That was supposed to be distopia, but to me at least it sounded more like eutopia!
so my advice personally is let groups, let society, let all those teams and clubs and cleaques and nations and other such associations wrot! put in the work to find a few decent individuals to be with, and realize that you do need them sometimes.