We are born completely helpless, totally dependent, without our cortex being developed enough to override our primitive and self-centered lower brain functions. But this is not enough to cause the condition of which we speak. Another aspect needs to be thrown into the mix.
We are born to caretakers of finite resources and imperfect abilities (our parents and teachers and other caregivers). And this means that our (perception of) infinite needs/wants must compete with the finite resources and imperfect abilities of our caretakers.
This, in turn, sets up a competition for those resources and abilities (a competition that is unnecessary but seems imperative at the time). And, again, that, in turn, sets up a situation to cause us to try to prove that we are more worthy than siblings/cousins/fellow students/etc.
We soon find out that if we can get our competition to look 'bad' it is easier than the effort it takes for us to look 'good'. So, we cast the blame for the broken window on our innocent but defenses little brother and he misses out on the ice cream dessert that evening, while we enjoy not only the fruit of the dairy section but also the satisfaction that it took less effort to make him look 'wrong' than it does for us to get an "A" on our spelling test.