This mentality is likely to be influenced by low self-esteem and perfectionism.
Descriptions of ugliness are very subjective, and this is likely to be just a knot in one's mind rather than an objective fact.
So why does this happen? I suspect there may be some perfectionist tendencies. Often, perfectionists will focus on their own "flaws", such as my eyes are too small, my smile doesn't look good, my face is not shaped well, etc. But other people may not even notice. But in fact, other people may not even notice these ah, these defects in your eyes is actually not as serious as you think. So instead of obsessing about these should be focused on other things, so that they are generous with others. Because the sunshine confident girl luck will not be too bad!