We’re all not aware of ourselves as we are aware of others. We can see someone else bashing themselves over some mistake and see how they’re being toxic to themselves, thinking “it’s just a small mistake, not a big deal, they can just try again and ignore it, why do they make such a big deal out of it?”… but then we can do exactly the same thing and not even notice it.

We are uniquely terrible at objectively rating our personal situation. Even just having some friends to do stuff with, like in this comic, is already average or even above average in “being lovable”. But the person in the comic might compare themselves with the most popular person around them, or they might want to be loved by one particular person by whom they are not, even if plenty of other people do or would love them.

We are really good at finding one bad thing about our lives and ignoring all the other good things we got going on, because the human psyche is wired to disproportionately focus on the bad instead of the good.

Without manual working against all these natural effects, the result is seen in the comic, an unhappy person that doesn’t really need to be unhappy. So no, this doesn’t require any particular trauma, this is just completely natural human behavior that almost anyone shows sometime in their lives. Some more, some less, depending on trauma, but can happen to anyone.