The way someone view themselves is subject to many variables that goes beyond these generalization.
If you've ever experienced any psychoactive drugs that induce euphoria and confidence such as cocaine and amphetamine, you will see yourself as a lot more attractive and smarter than you actually are. Now, ask that same person to rate themselves when they're going through withdrawal. You can bet that their self-perception won't be the same.
You might say that we're discussing this in the context of a normal person without any external influence. But that's the catch. There's no such thing as a normal person and we're always under the influence.
Get someone to rate their attractiveness when they're hungry, when they're full, when they're heartbroken, when they're in love, when they're socially anxious and depressed, when they're confident and outgoing. Even the best of us have many bad days.
There are structures in our brain that filters out what's deemed as "irrelevant information" and it's extremely difficult to view yourself objectively. Think of it as a kind of information tolerance, similar to drug tolerance.
If we can adapt to the putrid stench of hydrogen sulfide, you can bet we'll adapt to seeing our own flaw. Likewise, given enough time, most people will come to adapt to the various tragedies and good-fortune that befall upon them. The brain is remarkable at adapting.
How do you think someone who is lean and fit would react if they woke up extremely obese the next day? They would be a lot less complacent than a regular obese person because that person has had a lot time to adapt to their change of appearance.
What makes matter even more complicated is peer comments. Not to be crass, but have you ever came across a not-so-attractive girl on facebook getting tons of compliments from other women?
Those white lies are extremely insidious and I've always struggle with the fact that I can't judge myself objectively. This also goes the other way. There are some extremely beautiful people whose self-perception have been ruined by bullying and insults.
Think about the time when you first start wearing contacts or glasses, it takes a few days to get use to your own appearance.
Now take an extreme example with people undergoing plastic surgery. Even when the change is positive, some people are traumatize psychologically afterward because they're unable to reconcile with new face, but your brain seems to adapt regardless of whether or not the change is positive or negative. So this may lead to an issue of ambiguity, where you can't even tell if the change is positive or negative. A stranger will have a much easier time though, if only we can get them to stop sugar-coating.
Long ago when I told a girl that I thought she was beautiful. She truly couldn't believe me because from her POV, it's hard for some people to see themselves as beautiful when they've been looking at the same face for decades.
Some beautiful people also can't take compliments seriously from those they've considered are not beautiful, because they erroneously believe that because this person's standard is lower, that somehow their sense of aesthetic is not up to par.
One thing is for sure, it's not a good idea to take your mother's compliment seriously. Most mothers think that their son is handsome.
On the other hand, if your drunk buddies are reluctantly lamenting over the fact that they couldn't be born with your face, otherwise they would be so much more successful with women, then maybe you really are a handsome bastard.