I can only speak for what I have observed in my wife - but I think her case is quite typical.
She does not realize that the standards she is requiring of her self and others are way too high, unachievable and unrealistic. As a matter of fact she does not think of these overly high standards as being high at all - she thinks of them as being the lowest standards necessary to make something work. She does not see herself as perfect or even as aspiring to perfection. As a matter of fact, the truth is she thinks of herself quite lowly. In part that is a self-fulfilling prophecy and a cycle that is hard to break out of. But it all starts with her thinking too LOW of herself. She thinks she won't be good enough (for whatever) and so she imposes overly high standards on herself and others to insure her success. But of course the standards she is imposing on herself are too high, so she will inevitably fail. Once she has failed, she will think even less of herself and will impose even higher standards on herself. She is very much aware of her problem and suffers tremendously because of it, but she mistakenly thinks that her imposing overly high standards on herself would be the solution, when in actuality it is the cause for her problems. But of course it isn't the ultimate cause, the ultimate cause is her thinking too lowly of herself to begin with.
Wow all the "she" changed to "he" and "her" to "him" and it's A PERFECT FIT for my ocpd ex