[...] What I want to know is how difficult you find admitting your faults to yourself. What are your reactions to the person/people that tells you about yourself? Do you deny? Blame? Begin criticizing the other person to take the heat of yourself? [...]
I don't tend to see negative personal characteristics in a relationship as "faults." Instead I tend to see them as "relationship irritants." It's rare that personal characteristics are negative in all of one's relationships. More likely, individual personal characteristics are positive in some circumstances and relationships and negative in others.
For example:
1) Let's say I take command and run the show at work. That characteristic is admired and rewarded in the workplace by my bosses and coworkers (and even my subordinates). But at home, my wife insists that I'm pushy and make all the decisions and don't treat her as an equal. So that characteristic is a positive personal characteristic in the workplace but a relationship irritant in my marriage.
2) Let's say I spend a lot of time in bars drinking with my friends. It's a positive characteristic with my friends but a relationship irritant with my boss, who is tired of me showing up at work with hangovers or getting drunk over lunchtime.
3) Let's say my wife is more of a perfectionist than me; so when we do things together, I feel like she sucks the fun out of them by working too hard at them. But if we don't push for perfection, she gets bored or irritated that we're missing out on an important part of the experience. It's hard to say who is at "fault" in a situation like this.
4) And so on.
My feeling is that a lot of my personal characteristics are positive in one or more environments, but they don't necessarily translate well into a different environment. To be quiet and introverted may be great at work, but it isn't so great when I go out to social events. Or a personal characteristic of mine may be perfectly fine with my wife for the first five years of our marriage but then she starts complaining about it in the sixth year. Perhaps she says, "I always knew you were shy and bookish, but I thought you would grow out of it. I'm tired of this. We need to get out and start doing more social things."
I think this gets more into the real nature of relationships. It's usually not the case that a relationship is doomed by a single "fault" (or succeeds because of a lack of "faults"). You never really get rid of the "faults," because there are always new irritants cropping up in long-term relationships. There are always new strains. And since individual frictions usually only crop up in one relationship (at least initially) out of many in a given person's life, they may seem entirely subjective and arbitrary.
Rather it's my experience that, over the long-term, relationships fall into either a virtuous cycle of dealing successfully with routine irritants or into a vicious cycle of stumbling and struggling with routine irritants and frictions. IOW, I think it comes down to conflict resolution skills. How much leverage do we give key people in our life to change characteristics of ourselves? Do we dig in our heels? Do we insist on sharing the pain by demanding a reciprocal change from the other person?
(Not disagreeing with the OP; just restating it a bit.)
Anyway, my own answer: The wife and the boss get a lot of leeway to demand change from me. Friends--not so much, since they are more disposable. And meantime I work on the general concept of getting better at conflict resolution rather than worrying about individual "faults." I figure that if I can get the overall mechanism down, the details (the separate conflicts) will take care of themselves.
FL