A couple of thoughts.
I have found that when people come in to record, two things perversely happen simultaneously. The first is that they hear things that they don't like and spend a lot of time trying to fix when in fact those things are of absolutely no consequence to the listener, and the second is that, while they are fixing those things, they miss hearing things that are going to have a major impact, and most definitely need to be addressed (such as a vocal linbe being badly out of tune).
I can understand how your brain can tell you lies and convince you that all is well . . . so you hear what you what to hear rather than what is actually there. This often happens towards the end of a long session when you get tired and you want to be done with it.
Beng objective is really difficult because you can't un-know what you know. If you know you fluffed a note somewhere, you will be always be aware of its presence, even if a new listener wouldn't have a clue and wouldn't care either. But you get a semblance of objectivity by, for example, playing material in one room while doing something in another. That tends to hide trivialities but reveal major flaws.